drm/xe/tests: Fix printf format specifiers in xe_migrate test

KUNIT_FAIL() is used to fail the xe_migrate test when an error occurs.
However, there's a mismatch in the format specifier: '%li' is used to
log 'err', which is an 'int'.

Use '%i' instead of '%li', and for the case where we're printing an
error pointer, just use '%pe', instead of extracting the error code
manually with PTR_ERR(). (This also results in a nicer output when the
error code is known.)

Fixes: dd08ebf6 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: David Gow <davidgow@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>