drm/xe/gt: Fix min() with u32 and u64

Fix the following error while building for 32b:

	In file included from ../drivers/gpu/drm/xe/xe_gt.c:6:
	../drivers/gpu/drm/xe/xe_gt.c: In function ‘gt_ttm_mgr_init’:
	../include/linux/minmax.h:20:35: error: comparison of distinct pointer types lacks a cast [-Werror]
	   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
	      |                                   ^~

Cast it to u64 so size of the second operand matches the first one when
building it for 32 bits.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>