AMDGPU: Update elf flags in amdgpu-elf-flags.s
AMDGPU: Update elf flags in amdgpu-elf-flags.s

This is required after r325399:
  - EF_AMDGPU_ARCH_GCN got removed
  - In the test, EF_AMDGPU_ARCH_GCN is replaced with EF_AMDGPU_MACH_AMDGCN_GFX803


git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@325400 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld