[flang] Add one semantic check for procedure bind(C) interface-name

As Fortran 2018 C1521, in procedure declaration statement, if
proc-language-binding-spec (bind(c)) is specified, the proc-interface
shall appear, it shall be an interface-name, and interface-name shall
be declared with a proc-language-binding-spec.

Reviewed By: klausler, Jean Perier

Differential Revision: https://reviews.llvm.org/D127121