ARM/BFD: Correct an `index' global shadowing error

ARM/BFD: Correct an `index' global shadowing error

Fix a commit 5025eb7c0d87 ("Delete relocations associatesd with deleted
exidx entries.") build regression:

cc1: warnings being treated as errors
.../bfd/elf32-arm.c: In function 'elf32_arm_update_relocs':
.../bfd/elf32-arm.c:14951: warning: declaration of 'index' shadows a global declaration
/usr/include/string.h:304: warning: shadowed declaration is here
make[3]: *** [elf32-arm.lo] Error 1

in a way following commit 91d6fa6a035c ("Add -Wshadow to the gcc command
line options used when compiling the binutils.").

	bfd/
	* elf32-arm.c (elf32_arm_update_relocs): Rename `index' local
	variable to `reloc_index'.