NDS32/BFD: Correct an aliasing error in `nds32_elf_check_relocs'

NDS32/BFD: Correct an aliasing error in `nds32_elf_check_relocs'

Fix an aliasing build error:

cc1: warnings being treated as errors
.../bfd/elf32-nds32.c: In function 'nds32_elf_check_relocs':
.../bfd/elf32-nds32.c:6644: warning: dereferencing type-punned pointer will break strict-aliasing rules
make[3]: *** [elf32-nds32.lo] Error 1

in a way following commit 6edfbbad0864 ("Fix up gcc4.1 aliasing
warnings"), <https://sourceware.org/ml/binutils/2005-10/msg00071.html>.

	bfd/
	* elf32-nds32.c (nds32_elf_check_relocs): Avoid aliasing warning
	from GCC.