LoongArch: Fix PLT entry generate bug

If a function symbol only get its address by la.global, without
directly called by bl instruction, the PLT entry is not required.

bfd/ChangeLog:

	* elfnn-loongarch.c (loongarch_elf_adjust_dynamic_symbol): Fix PLT
	entry generate bug.

ld/ChangeLog:

	* testsuite/ld-elf/shared.exp: Clear xfail for LoongArch.
2 files changed