[InstrProfiling] Mark __llvm_profile_instrument_target last parameter as i32...

[InstrProfiling] Mark __llvm_profile_instrument_target last parameter as i32 zeroext if appropriate.

On some architectures (s390x, ppc64, sparc64, mips), C-level int is passed
as i32 signext instead of plain i32.  Likewise, unsigned int may be passed
as i32, i32 signext, or i32 zeroext depending on the platform.  Mark
__llvm_profile_instrument_target properly (its last parameter is unsigned
int).

This (together with the clang change) makes compiler-rt profile testsuite pass
on s390x.

Differential Revision: http://reviews.llvm.org/D21736

llvm-svn: 287534