[Bindings][Go] Fixed go.test failure due to C-API argument type mismatch.

go.test was failing previously with error,
Command Output (stderr):
dibuilder.go:301: cannot use C.uint(t.Encoding) (type C.uint) as type
C.LLVMDWARFTypeEncoding in argument to func literal
This patch fixes the argument type.

Patch by Chirag (Chirag Patel)

Differential Revision: https://reviews.llvm.org/D51721

llvm-svn: 341680