[AMDGPU] table-driven parser/printer for amd_kernel_code_t structure fields

This is going to be used in .hsatext disassembler and can be used
in current assembler parser (lit tests passed on parsing).
Code using this helpers isn't included in this patch.

Benefits:

unified approach
fast field name lookup on parsing
Later I would like to enhance some of the field naming/syntax using this code.

Patch by: Valery Pykhtin

Differential Revision: http://reviews.llvm.org/D17150

llvm-svn: 262473