[AMD] Reland "Add gfx950 target definitions" (#5392)

This relands #5392
to enable new arch target since backend support has been
added--it doesn't depend on the reverted LLVM upgrade in
#5341; basic
necessary enablement is already included in the current llvm
version we're using.

third_party/amd/backend/include/hsa/amd_hsa_elf.h

@@ -136,7 +136,7 @@ enum : unsigned {
   EF_AMDGPU_MACH_AMDGCN_GFX942        = 0x04c,
   EF_AMDGPU_MACH_AMDGCN_RESERVED_0X4D = 0x04d,
   EF_AMDGPU_MACH_AMDGCN_GFX1201       = 0x04e,
-  EF_AMDGPU_MACH_AMDGCN_RESERVED_0X4F = 0x04f,
+  EF_AMDGPU_MACH_AMDGCN_GFX950        = 0x04f,
   EF_AMDGPU_MACH_AMDGCN_RESERVED_0X50 = 0x050,
   EF_AMDGPU_MACH_AMDGCN_GFX9_GENERIC      = 0x051,
   EF_AMDGPU_MACH_AMDGCN_GFX10_1_GENERIC   = 0x052,

third_party/amd/lib/TritonAMDGPUToLLVM/TargetUtils.cpp

@@ -11,6 +11,7 @@ ISAFamily deduceISAFamily(llvm::StringRef arch) {
 
   // CDNA ISA cases
   switch (kind) {
+  case llvm::AMDGPU::GK_GFX950:
   case llvm::AMDGPU::GK_GFX942:
   case llvm::AMDGPU::GK_GFX941:
   case llvm::AMDGPU::GK_GFX940: