[openacc, libgomp, testsuite] Xfail declare-5.f90

[openacc, libgomp, testsuite] Xfail declare-5.f90

We're currently running into:
...
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O0  execution test
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O1  execution test
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O2  execution test
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O3 -fomit-frame-pointer \
  -funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O3 -g  execution test
FAIL: libgomp.oacc-fortran/declare-5.f90 -DACC_DEVICE_TYPE_nvidia=1 \
  -DACC_MEM_SHARED=0 -foffload=nvptx-none  -Os  execution test
...

A PR was filed for this: PR92790 - "[OpenACC] declare device_resident -
Fortran common blocks not handled / libgomp.oacc-fortran/declare-5.f90 fails"

Xfail the fails.

Tested on x86_64-linux with nvptx accelerator.

libgomp/ChangeLog:

2020-10-06  Tom de Vries  <tdevries@suse.de>

	* testsuite/libgomp.oacc-fortran/declare-5.f90: Add xfail for PR92790.