binutils/readelf: handle AMDGPU relocation types

binutils/readelf: handle AMDGPU relocation types

Make readelf recognize AMDGPU relocation types, as documented here:

  https://llvm.org/docs/AMDGPUUsage.html#amdgpu-relocation-records

The user-visible change looks like:

    -000000000004  000400000001 unrecognized: 1       0000000000000000 SCRATCH_RSRC_DWORD0
    -00000000000c  000500000001 unrecognized: 1       0000000000000000 SCRATCH_RSRC_DWORD1
    -000000000014  000600000007 unrecognized: 7       0000000000000000 global_var0
    -00000000001c  000700000008 unrecognized: 8       0000000000000000 global_var1
    -000000000024  000800000009 unrecognized: 9       0000000000000000 global_var2
    -00000000002c  00090000000a unrecognized: a       0000000000000000 global_var3
    -000000000034  000a0000000b unrecognized: b       0000000000000000 global_var4
    +000000000004  000400000001 R_AMDGPU_ABS32_LO 0000000000000000 SCRATCH_RSRC_DWORD0
    +00000000000c  000500000001 R_AMDGPU_ABS32_LO 0000000000000000 SCRATCH_RSRC_DWORD1
    +000000000014  000600000007 R_AMDGPU_GOTPCREL 0000000000000000 global_var0
    +00000000001c  000700000008 R_AMDGPU_GOTPCREL 0000000000000000 global_var1
    +000000000024  000800000009 R_AMDGPU_GOTPCREL 0000000000000000 global_var2
    +00000000002c  00090000000a R_AMDGPU_REL32_LO 0000000000000000 global_var3
    +000000000034  000a0000000b R_AMDGPU_REL32_HI 0000000000000000 global_var4

binutils/ChangeLog:

	* readelf.c (dump_relocations): Handle EM_AMDGPU.

include/ChangeLog:

	* elf/amdgpu.h: Add relocation values.

Change-Id: I2ed4589f4cd37ea11ad2e0cb38d4b682271e1334