gfortran.dg/compiler-directive_2.f: Update dg-error

This is a fallout of commit r15-2378-g29b1587e7d3466
  OpenMP/Fortran: Fix handling of 'declare target' with 'link' clause [PR115559]
where the '!GCC$' attributes were added in reverse order.
Result: The error diagnostic for the stdcall/fastcall was reversed.
Solution: Swap the order in dg-error.

gcc/testsuite/ChangeLog:

	* gfortran.dg/compiler-directive_2.f: Update dg-error.