Drop include guard from SPIRVErrorEnum.h

SPIRVErrorEnum.h is included multiple times, and the include guard
caused the SPIRVErrorMap (which is the second inclusion of
SPIRVErrorEnum.h in SPIRVError.h) to remain empty.

Author: svenvh

lib/SPIRV/libSPIRV/SPIRVErrorEnum.h

@@ -1,6 +1,3 @@
-#ifndef SPIRV_LIBSPIRV_SPIRVERRORENUM_H
-#define SPIRV_LIBSPIRV_SPIRVERRORENUM_H
-
 /* The error code name should be meaningful since it is part of error message */
 _SPIRV_OP(Success, "")
 _SPIRV_OP(InvalidTargetTriple,
@@ -10,5 +7,3 @@ _SPIRV_OP(InvalidMemoryModel, "Expects 0-3.")
 _SPIRV_OP(InvalidFunctionControlMask, "")
 _SPIRV_OP(InvalidBuiltinSetName, "Expects OpenCL.std.")
 _SPIRV_OP(InvalidFunctionCall, "Unexpected llvm intrinsic:")
-
-#endif