[clang] [llvm] [AMDGPU] Define new target gfx1154 (PR #204816)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> 'generic' targets are not used on graphics side as far as I know. All gfx117x targets are identical at the moment. If someone asks for a generic one we can add it.

I am asking and this really should be the only way targets are defined. In the absence of the ISA being properly versioned, every incompatible ISA change should come with a new generic target 






https://github.com/llvm/llvm-project/pull/204816