RISC-V: Adding B ext, fp16 and missing scalar instruction type for sifive-7 pipeline...

RISC-V: Adding B ext, fp16 and missing scalar instruction type for sifive-7 pipeline model [PR120659]

gcc/ChangeLog:

	PR target/120659
	* config/riscv/sifive-7.md: Add B extension, fp16 and missing
	scalar instruction type for sifive-7 pipeline model.

gcc/testsuite/ChangeLog:

	PR target/120659
	* gcc.target/riscv/pr120659.c: New test.