RISC-V: Added vendor extensions, xmipscbop, xmipscmov, xmipsexectl and xmipslsp

Spec:
https://mips.com/wp-content/uploads/2025/03/P8700-F_Programmers_Reference_Manual_Rev1.82_3-19-2025.pdf

Added MIPS vendor extensions, xmipscbop, xmipscmov, xmipsexectl and xmipslsp
with verison 1.0.

Passed binutils testsuites of targets elf32/elf64/linux32/linux64.

Signed-off-by: Jovan Dmitrović <jovan.dmitrovic@htecgroup.com>
Signed-off-by: Chao-ying Fu <cfu@wavecomp.com>