drm/i915/migrate: don't check the scratch page

drm/i915/migrate: don't check the scratch page

[ Upstream commit 8eb7fcce34d16f77ac8efa80e8dfecec2503e8c5 ]

The scratch page might not be allocated in LMEM(like on DG2), so instead
of using that as the deciding factor for where the paging structures
live, let's just query the pt before mapping it.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211206112539.3149779-1-matthew.auld@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>