LoongArch: Make align symbol be in same section with alignment directive

LoongArch: Make align symbol be in same section with alignment directive

R_LARCH_ALIGN (psABI v2.30) requires a symbol index. The symbol is only
created at the first time to handle alignment directive. This means that
all other sections may use this symbol. If the section of this symbol is
discarded, there may be problems. Search it in its own section.

Remove elf_backend_data.is_rela_normal() function added at commit daeda14191c.

Co-authored-by: Jinyang He <hejinyang@loongson.cn>
Reported-by: WANG Xuerui <git@xen0n.name>
Link: https://lore.kernel.org/loongarch/2abbb633-a10e-71cc-a5e1-4d9e39074066@loongson.cn/T/#t