fortran: Fix invalid function decl clobber ICE [PR105012]

fortran: Fix invalid function decl clobber ICE [PR105012]

The fortran frontend, as result symbol for a function without
declared result symbol, uses the function symbol itself.  This caused
an invalid clobber of a function decl to be emitted, leading to an
ICE, whereas the intended behaviour was to clobber the function result
variable.  This change fixes the problem by getting the decl from the
just-retrieved variable reference after the call to
gfc_conv_expr_reference, instead of copying it from the frontend symbol.

	PR fortran/105012

gcc/fortran/ChangeLog:

	* trans-expr.cc (gfc_conv_procedure_call): Retrieve variable
	from the just calculated variable reference.

gcc/testsuite/ChangeLog:

	* gfortran.dg/intent_out_15.f90: New test.