Fix broken HUGE_VALF macro in llvm-c/DataTypes.h

Commit 3a29393b4709d15069130119cf1d136af4a92d77 removes the cmath/math.h
includes from the DataTypes.h header to speed up parsing. However the
DataTypes.h header was using this header to get the macro `HUGE_VAL` for its own
`HUGE_VALF` macro definition. Now the macro instead just expands into a plain
`HUGE_VAL` token which leads to compiler errors unless `math.h` was previously
included by the including source file. It also leads to compiler warnings with
enabled module builds which point out this inconsistency.

The correct way to fix this seems to be to just remove HUGE_VALF from the
header. llvm-c is not referencing that macro from what I can see and users
probably should just include the math headers if they need it (or define it on
their own for really old C versions).

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D83761

include/llvm-c/DataTypes.h

@@ -77,8 +77,4 @@ typedef signed int ssize_t;
 # define UINT64_MAX 0xffffffffffffffffULL
 #endif
 
-#ifndef HUGE_VALF
-#define HUGE_VALF (float)HUGE_VAL
-#endif
-
 #endif /* LLVM_C_DATATYPES_H */