Resolve ICE in 'gcc/fortran/trans-openmp.cc:gfc_omp_call_is_alloc'

Resolve ICE in 'gcc/fortran/trans-openmp.cc:gfc_omp_call_is_alloc'

Fix-up for recent commit 2505a8b41d3b74a545755a278f3750a29c1340b6
"OpenMP: Minor '!$omp allocators' cleanup", which caused:

    {+FAIL: gfortran.dg/gomp/allocate-5.f90   -O  (internal compiler error: tree check: expected class 'type', have 'declaration' (function_decl) in gfc_omp_call_is_alloc, at fortran/trans-openmp.cc:8386)+}
    [-PASS:-]{+FAIL:+} gfortran.dg/gomp/allocate-5.f90   -O  (test for excess errors)

..., and similarly in 'libgomp.fortran/allocators-1.f90',
'libgomp.fortran/allocators-2.f90', 'libgomp.fortran/allocators-3.f90',
'libgomp.fortran/allocators-4.f90', 'libgomp.fortran/allocators-5.f90'.

	gcc/fortran/
	* trans-openmp.cc (gfc_omp_call_is_alloc): Resolve ICE.