drm/xe/tests/pci: Convert GT count check to general device check

drm/xe/tests/pci: Convert GT count check to general device check

We already have check_graphics_ip() and check_media_ip() as general
functions to check the IP descriptors.  The check in
check_platform_gt_count() is simple enough such that we can convert the
function to a more general device check.  In an upcoming change, we will
also add some checks for other members of struct xe_device_desc. As
such, rename check_platform_gt_count() to check_platform_desc().

While at it, use inline (unsigned int) casting of max_gt_per_tile to
keep checks for each member localized; and use KUNIT_EXPECT_*() variants
of the macros to allow multiple issues to be reported.

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20251020-xe-kunit-dma_mask_size-va_bits-vm_max_level-v2-1-27b03971bc7e@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>