Revert "Map FPFastMathModeINTEL on SPV_INTEL_fp_fast_math_mode (#2360)" (#12923)

This reverts commit 339c1c6.

It's a good-tiny fix, but we have to revert it for now.

Author: MrSidims

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVEntry.h

@@ -904,8 +904,6 @@ class SPIRVCapability : public SPIRVEntryNoId<OpCapability> {
       return ExtensionID::SPV_INTEL_fast_composite;
     case internal::CapabilitySubgroupRequirementsINTEL:
       return ExtensionID::SPV_INTEL_subgroup_requirements;
-    case CapabilityFPFastMathModeINTEL:
-      return ExtensionID::SPV_INTEL_fp_fast_math_mode;
     default:
       return {};
     }

llvm-spirv/test/extensions/INTEL/SPV_INTEL_fp_fast_math_mode/fp_contract_reassoc_fast_mode.ll

@@ -5,14 +5,12 @@
 ; RUN: llvm-spirv -r %t.spv -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-LLVM
 
 ; CHECK-SPIRV-ON: 2 Capability FPFastMathModeINTEL
-; CHECK-SPIRV-ON: SPV_INTEL_fp_fast_math_mode
 ; CHECK-SPIRV-ON: 3 Name [[mu:[0-9]+]] "mul"
 ; CHECK-SPIRV-ON: 3 Name [[su:[0-9]+]] "sub"
 ; CHECK-SPIRV-ON-DAG: 4 Decorate [[mu]] FPFastMathMode 65536
 ; CHECK-SPIRV-ON-DAG: 4 Decorate [[su]] FPFastMathMode 131072
 
 ; CHECK-SPIRV-OFF-NOT: 2 Capability FPFastMathModeINTEL
-; CHECK-SPIRV-OFF-NOT: SPV_INTEL_fp_fast_math_mode
 ; CHECK-SPIRV-OFF: 3 Name [[mu:[0-9]+]] "mul"
 ; CHECK-SPIRV-OFF: 3 Name [[su:[0-9]+]] "sub"
 ; CHECK-SPIRV-OFF-NOT: 4 Decorate [[mu]] FPFastMathMode 65536