[OpenMP] Fix incorrect interop type for number of dependencies

The interop types use the number of dependencies in the function
interface. Every other function uses an `i32` to count the number of
dependencies except for the initialization function. This leads to
codegen issues when the rest of the compiler passes in an `i32` that
then creates an invalid call. Fix this to be consistent with the other
uses.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D150156