Improve Intel MIC offloading XFAILing for 'omp_get_device_num'

Improve Intel MIC offloading XFAILing for 'omp_get_device_num'

After recent commit be661959a6b6d8f9c3c8608a746789e7b2ec3ca4
"libgomp/testsuite: Improve omp_get_device_num() tests", we're now iterating
over all OpenMP target devices.  Intel MIC (emulated) offloading still doesn't
properly implement device-side 'omp_get_device_num', and we thus regress:

    PASS: libgomp.c/../libgomp.c-c++-common/target-45.c (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.c/../libgomp.c-c++-common/target-45.c execution test

    PASS: libgomp.c++/../libgomp.c-c++-common/target-45.c (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.c++/../libgomp.c-c++-common/target-45.c execution test

    PASS: libgomp.fortran/target10.f90   -O0  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -O0  execution test
    PASS: libgomp.fortran/target10.f90   -O1  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -O1  execution test
    PASS: libgomp.fortran/target10.f90   -O2  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -O2  execution test
    PASS: libgomp.fortran/target10.f90   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
    PASS: libgomp.fortran/target10.f90   -O3 -g  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -O3 -g  execution test
    PASS: libgomp.fortran/target10.f90   -Os  (test for excess errors)
    [-PASS:-]{+FAIL:+} libgomp.fortran/target10.f90   -Os  execution test

Improve the XFAILing added in commit bb75b22aba254e8ff144db27b1c8b4804bad73bb
"Allow matching Intel MIC in OpenMP 'declare variant'" for the case that *any*
Intel MIC offload device is available.

	libgomp/
	* testsuite/libgomp.c-c++-common/on_device_arch.h
	(any_device_arch, any_device_arch_intel_mic): New.
	* testsuite/lib/libgomp.exp
	(check_effective_target_offload_device_any_intel_mic): New.
	* testsuite/libgomp.c-c++-common/target-45.c: Use it.
	* testsuite/libgomp.fortran/target10.f90: Likewise.