tests/i915/gem_media_vme : skip on no media Samplers

Media samplers are not present on some of Gen11 platforms adding
skip on EHL and JSL as per Bspec.

Bspec:29151

Changes since V1 :
        Moved this skip check to igt_get_media_vme_func.[Tony Ye]

CC: Tony Ye <tony.ye@intel.com>
Signed-off-by: Mastan Katragadda <mastanx.katragadda@intel.com>
Reviewed-by: Tony Ye <tony.ye@intel.com>