drm/xe/vf: Fix GuC FW check for VF migration support

drm/xe/vf: Fix GuC FW check for VF migration support

The check whether GuC ABI version meets requirements shall be
performed after said version is received from GuC.

Doing it in wrong order was triggering a warning:
xe 0000:00:02.1: [drm] Assertion `gt->sriov.vf.guc_version.major` failed!

With this change, dislodge part of the VF migration support check
and moved it to after GuC handshake.

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Tested-by: Matthew Brost <matthew.brost@intel.com> #v1
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6349
Fixes: ff1d2b5e3d28 ("drm/xe: Read VF GMD_ID with a specifically-allocated dummy GT")
Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20251021224817.1593817-3-tomasz.lis@intel.com