LoongArch: set PRSTATUS_SIZE=0x1e0 to match kernel's struct elf_prstatus size

As PRSTATUS_SIZE is now with the value 0x1d8, which causes inconsistency with the kernel
definition and then can not lead to the correct branch for loongarch64 backend.

With the correct value 0x1e0 for the master branch, the loongarch64 banckend will work well.

Signed-off-by: Li Jian <lijian1@kylinos.cn>