gdb: LoongArch: Handle newly added llsc instructions

We can't put a breakpoint in the middle of a ll/sc atomic sequence,
handle the instructions sc.q, llacq.{w/d}, screl.{w/d} newly added
in the LoongArch Reference Manual v1.10 so a ll/sc atomic sequence
using them won't loop forever being debugged.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>