[AMDGPU] Fix GFX90x check prefixes in tests (#92254)

Author: jayfoad

llvm/test/CodeGen/AMDGPU/agpr-register-count.ll

@@ -157,10 +157,8 @@ declare void @undef_func()
 ; GFX908: .amdhsa_next_free_vgpr 32
 ; GFX90A: .amdhsa_next_free_vgpr 64
 ; GFX90A: .amdhsa_accum_offset 32
-; GCN908: NumVgprs: 128
-; GCN908: NumAgprs: 128
-; GCN90A: NumVgprs: 256
-; GCN90A: NumAgprs: 256
+; GCN:    NumVgprs: 32
+; GCN:    NumAgprs: 32
 ; GFX908: TotalNumVgprs: 32
 ; GFX90A: TotalNumVgprs: 64
 ; GFX908: VGPRBlocks: 7

llvm/test/CodeGen/AMDGPU/spill-vgpr.ll

@@ -88,8 +88,8 @@ define amdgpu_kernel void @max_10_vgprs_spill_v32(ptr addrspace(1) %p) #0 {
 ; GFX900: ScratchSize: 132
 ; GFX908: NumVgprs: 252
 ; GFX908: ScratchSize: 0
-; GCN900:    VGPRBlocks: 63
-; GCN908:    VGPRBlocks: 62
+; GFX900:    VGPRBlocks: 63
+; GFX908:    VGPRBlocks: 62
 ; GFX900:    NumVGPRsForWavesPerEU: 256
 ; GFX908:    NumVGPRsForWavesPerEU: 252
 define amdgpu_kernel void @max_256_vgprs_spill_9x32(ptr addrspace(1) %p) #1 {