LoongArch: Record pc instead of offset in la_abs relocation

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>

Author: heiher

arch/loongarch/include/asm/asmmacro.h

@@ -609,8 +609,7 @@
 	lu32i.d	\reg, 0
 	lu52i.d	\reg, \reg, 0
 	.pushsection ".la_abs", "aw", %progbits
-	768:
-	.dword	768b-766b
+	.dword	766b
 	.dword	\sym
 	.popsection
 #endif

arch/loongarch/include/asm/setup.h

@@ -25,7 +25,7 @@ extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len
 #ifdef CONFIG_RELOCATABLE
 
 struct rela_la_abs {
-	long offset;
+	long pc;
 	long symvalue;
 };
 

arch/loongarch/kernel/relocate.c

@@ -52,7 +52,7 @@ static inline void __init relocate_absolute(long random_offset)
 	for (p = begin; (void *)p < end; p++) {
 		long v = p->symvalue;
 		uint32_t lu12iw, ori, lu32id, lu52id;
-		union loongarch_instruction *insn = (void *)p - p->offset;
+		union loongarch_instruction *insn = (void *)p->pc;
 
 		lu12iw = (v >> 12) & 0xfffff;
 		ori    = v & 0xfff;