Enable to link ARM object file that hasn't attribute section.

Enable to link ARM object file that hasn't attribute section.

bfd/ChangeLog

2014-11-20  Terry Guo  <terry.guo@arm.com>

	* elf32-arm.c (elf32_arm_merge_eabi_attributes): Skip if input bfd
	hasn't attribute section.

ld/testsuite/ChangeLog:

2014-11-20  Terry Guo  <terry.guo@arm.com>

	* ld-arm/attr-merge-nosection-1.d: New file.
	* ld-arm/attr-merge-nosection-1a.s: Likewise.
	* ld-arm/attr-merge-nosection-1b.s: Likewise.
	* ld-arm/arm-elf.exp: Include the new test.