drm/i915/selftests: handle object rounding

Ensure we account for any object rounding due to min_page_size
restrictions.

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/20211206112539.3149779-4-matthew.auld@intel.com

drivers/gpu/drm/i915/gt/selftest_migrate.c

@@ -49,6 +49,7 @@ static int copy(struct intel_migrate *migrate,
 	if (IS_ERR(src))
 		return 0;
 
+	sz = src->base.size;
 	dst = i915_gem_object_create_internal(i915, sz);
 	if (IS_ERR(dst))
 		goto err_free_src;