LoongArch: Fixed R_LARCH_[32/64]_PCREL generation bug

The enum BFD_RELOC_[32/64] was mistakenly used in the macro instead
of the relocation in fixp. This can cause the second relocation
of a pair to be deleted when -mthin-add-sub is enabled. Apply the
correct macro to fix this.

Also sets the initial value of -mthin-add-sub.
4 files changed