[AMDGPU] Kernel arg metadata: added support for "__hip_texture" type.

[AMDGPU] Kernel arg metadata: added support for "__hip_texture" type.

Summary:
Hip texture type is equivalent to OpenCL image. So, we need to set the Image type for kernel arguments with __hip_texture type.

Differential revision: https://reviews.llvm.org/D63850

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365073 91177308-0d34-0410-b5e6-96231b3b80d8