media: staging/intel-ipu3: Fix memory leak in imu_fmt

We are losing the reference to an allocated memory if try. Change the
order of the check to avoid that.

Cc: stable@vger.kernel.org
Fixes: 6d5f26f2 ("media: staging/intel-ipu3-v4l: reduce kernel stack usage")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>