[AMDGPU] llvm-objdump: Minimal HSA Code Object disassembler support.

Reenable reverted r265550 with endianness issue fixed. Variables of
endian-aware types such as ulittle32_t should be explicitly casted
to their natural equivalent types before passing it as vararg to
printf like functions (format in my case). Added lit config file
depending on AMDGPU target as the testcase uses assembler.

Differential revision: http://reviews.llvm.org/D16998

llvm-svn: 265645