riscv: add ISA extension parsing for Zilsd and Zclsd

riscv: add ISA extension parsing for Zilsd and Zclsd

Add parsing for Zilsd and Zclsd ISA extensions which were ratified in
commit f88abf1 ("Integrating load/store pair for RV32 with the
main manual") of the riscv-isa-manual.

Signed-off-by: Pincheng Wang <pincheng.plct@isrc.iscas.ac.cn>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Link: https://patch.msgid.link/20250826162939.1494021-3-pincheng.plct@isrc.iscas.ac.cn
[pjw@kernel.org: cleaned up checkpatch issues, whitespace; updated to apply]
Signed-off-by: Paul Walmsley <pjw@kernel.org>