media: uvcvideo: Fix memory leak of object map on error exit path

Currently when the allocation of map->name fails the error exit path
does not kfree the previously allocated object map. Fix this by
setting ret to -ENOMEM and taking the free_map exit error path to
ensure map is kfree'd.

Addresses-Coverity: ("Resource leak")

Fixes: 70fa906d

 ("media: uvcvideo: Use control names from framework")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>