sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

random(4): Reorder configuration of random source modules

Move fast entropy source registration to the earlier
SI_SUB_RANDOM:SI_ORDER_FOURTH and move random_harvestq_prime after that.
Relocate the registration routines out of the much later randomdev module
and into random_harvestq.

This is necessary for the fast random sources to actually register before we
perform random_harvestq_prime() early in the kernel boot.

No functional change.

Reviewed by: delphij, markjm
Approved by: secteam(delphij)
Differential Revision: https://reviews.freebsd.org/D21308

random: Add PowerPC 'darn' instruction entropy source

Summary:
PowerISA 3.0 adds a 'darn' instruction to "deliver a random number". This
driver was modeled after (rather, copied and gutted of) the Ivy Bridge
rdrand driver.

This uses the "Conditional Random Number" behavior to remove input bias.

From the ISA reference the 'darn' instruction, and the random number
generator backing it, conforms to the NIST SP800-90B and SP800-90C
standards, compliant to the extent possible at the time the hardware was
designed, and guarantees a minimum 0.5 bits of entropy per bit returned.

Reviewed By: markm, secteam (delphij)
Approved by: secteam (delphij)
Differential Revision: https://reviews.freebsd.org/D16552