s390/tools: fix gcc 8 stringop-truncation warnings

Replace strncpy which has been used to copy a substring into buf
without NUL-termination with memcpy to avoid the following gcc 8
warnings:

arch/s390/tools/gen_opcode_table.c: In function ‘add_to_group.isra.4’:
arch/s390/tools/gen_opcode_table.c:260:2: warning: ‘strncpy’
output may be truncated copying 2 bytes from a string of length 19
[-Wstringop-truncation]
strncpy(group->opcode, insn->opcode, 2);

In function ‘print_opcode_table’,
inlined from ‘main’ at arch/s390/tools/gen_opcode_table.c:333:2:
arch/s390/tools/gen_opcode_table.c:286:4: warning: ‘strncpy’
output may be truncated copying 2 bytes from a string of length 19
[-Wstringop-truncation]
strncpy(opcode, insn->opcode, 2);

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

s390/tools: generate header files in arch/s390/include/generated/

Previously, the generated dis.h and facilities.h header files have been
stored in include/generated. Because they are s390 specific, store them
in the arch/s390/include/generated/asm/ directory. Also update
references to the header files respectively.

To prevent name collisions with those header files in asm/ that
include the generated ones, rename the generated headers files
and add an -defs suffix. Also update the generators to create
the ifdef guards respectively.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

s390: add a few more SPDX identifiers

Add the correct SPDX license to a few more files under arch/s390 and
drivers/s390 which have been missed to far.
The SPDX identifier is a legally binding shorthand, which can be used
instead of the full boiler plate text.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

s390/disassembler: generate opcode tables from text file

The current way of adding new instructions to the opcode tables is
painful and error prone. Therefore add, similar to binutils, a text
file which contains all opcodes and the corresponding mnemonics and
instruction formats.

A small gen_opcode_table tool then generates a header file with the
required enums and opcode table initializers at the prepare step of
the kernel build.

This way only a simple text file has to be maintained, which can be
rather easily extended.

Unlike before where there were plenty of opcode tables and a large
switch statement to find the correct opcode table, there is now only
one opcode table left which contains all instructions. A second opcode
offset table now contains offsets within the opcode table to find
instructions which have the same opcode prefix. In order to save space
all 1-byte opcode instructions are grouped together at the end of the
opcode table. This is also quite similar to like it was before.

In addition also move and change code and definitions within the
disassembler. As a side effect this reduces the size required for the
code and opcode tables by ~1.5k.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>