[AMDGPU] Use tablegen for argument indices

Use tablegen generic tables to get the index of image intrinsic
arguments.
Before, the computation of which image intrinsic argument is at which
index was scattered in a few places, tablegen, the SDag instruction
selection and GlobalISel. This patch changes that, so only tablegen
contains code to compute indices and the ImageDimIntrinsicInfo table
provides these information.

Differential Revision: https://reviews.llvm.org/D86270