LoongArch: Record pc instead of offset in la_abs relocation

LoongArch: Record pc instead of offset in la_abs relocation

[ Upstream commit aa0cbc1b506b090c3a775b547c693ada108cc0d7 ]

To clarify, the previous version functioned flawlessly. However, it's
worth noting that the LLVM's LoongArch backend currently lacks support
for cross-section label calculations. With this patch, we enable the use
of clang to compile relocatable kernels.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Sasha Levin <sashal@kernel.org>