aarch64: Allow PC-relative relocations against protected STT_FUNC for -shared

aarch64: Allow PC-relative relocations against protected STT_FUNC for -shared

    __attribute__((visibility("protected"))) void *foo() {
      return (void *)foo;
    }

gcc -fpic -shared -fuse-ld=bfd fails with the confusing diagnostic:

    relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `foo' which may bind externally can not be used when making a shared object; recompile with -fPIC

Call _bfd_elf_symbol_refs_local_p with local_protected==true to suppress
the error.  The new behavior matches gold and ld.lld.

Note: if some code tries to use direct access relocations to take the
address of foo (likely due to -fno-pic), the pointer equality will
break, but the error should be reported on the executable link, not on
the innocent shared object link.  glibc 2.36 will give a warning at
relocation resolving time.