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

Remove /^/[*/]\s*\$FreeBSD\$.*\n/

Add full softfloat and hardfloat support for RISC-V.

Hardfloat is now default (use riscv64sf as TARGET_ARCH
for softfloat).

Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D8529