[flang] Consider bind(c) when lowering calls to intrinsic module procedures (#70386)

When attempting to lower an intrinsic module procedure call, take into
account bind(c). Such procedures cannot be lowered as intrinsics since
their implementation is external to the module.

With this solution, the hardcoded "omp_lib" string can be removed when
checking if intrinsic module procedure since all procedure interfaces in
that module use bind(c).