[LoongArch] Use R_LARCH_ALIGN with section symbol (#84741)

In LoongArch psABI v2.30, the R_LARCH_ALIGN requires symbol index to
support the third parameter of alignment directive. Create symbol for
each section is redundant because they have section symbol which can
also be used as symbol index. So use section symbol directly for
R_LARCH_ALIGN.