build: Define _BOOT_MODE once and for all in ArchitectureRules+BootRules.

Previously it was spread all around the tree, and was not defined
consistently for all boot objects (there were a number of boot modules
which did not define it, but did include headers which checked for it.)

Now, as it is handled in SetupBoot which is invoked for all boot objects,
it will be applied consistently throughout. We can thus drop the manual
additions of it from all Jamfiles.

boot/efi: factor out generic mmu functions

This change moves the common functions related to EFI memory map
to arch/generic for arm, arm64, x86.

riscv64 and x86_64 shall be handled separately as they use some
more architecture-specific logic:
* riscv64 needs special treatment for the M-mode resident code
located at 0x80000000 which is reported as available in the
EFI memory map provided by u-boot.
* x86_64 has a slightly different logic for building the
memory regions list so some additional rework and testing will be
needed before it can be unified with the generic mmu functions.

Change-Id: I430c84dfc693c5b6f04c170dec8ffb1db2c2ace1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5694
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

boot/efi/x86: implement SMP detection and bootup

* move common SMP initialization code to x86/arch_smp.cpp

* factor out arch-specific SMP initialization to
arch_smp_32.cpp resp arch_smp_64.cpp

* implement smp_trampoline for x86 32-bit EFI loader

* rename SMP trampoline for x86_64 to long_smp_trampoline

* add new argument virtKernelArgs to arch_smp_boot_other_cpus
as the kernel args are not identity mapped on 32-bit architectures

Change-Id: I30d0bb1fa9bfb08f6784a2af34eb83d6b64afa57
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4869
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>

boot/efi/x86: implement MMU initialization and jump to kernel

Change-Id: Ie42c69f3851acae3a8184aa97ab2dd01c9485f46
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4850
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

boot/efi: add stubs for x86

Change-Id: I8d3dfa7cc07679a8b024df24f7cddb3a5bcec02c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4747
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>