ANDROID: android-verity: do not compile as independent module

ANDROID: android-verity: do not compile as independent module

dm-android-verity depends on optional kernel command line parameters.
When compiled as module the __setup macro ends up being a no-op
resulting in the following warnings:

/work/build/batch/drivers/md/dm-android-verity.c:91:19: warning: 'verity_buildvariant' defined but not used [-Wunused-function]
 static int __init verity_buildvariant(char *line)
                   ^~~~~~~~~~~~~~~~~~~
/work/build/batch/drivers/md/dm-android-verity.c:83:19: warning: 'verity_keyid_param' defined but not used [-Wunused-function]
 static int __init verity_keyid_param(char *line)
                   ^~~~~~~~~~~~~~~~~~
/work/build/batch/drivers/md/dm-android-verity.c:75:19: warning: 'verity_mode_param' defined but not used [-Wunused-function]
 static int __init verity_mode_param(char *line)
                   ^~~~~~~~~~~~~~~~~
/work/build/batch/drivers/md/dm-android-verity.c:67:19: warning: 'verified_boot_state_param' defined but not used [-Wunused-function]
 static int __init verified_boot_state_param(char *line)
                   ^~~~~~~~~~~~~~~~~~~~~~~~~
Tested with allmodconfig.

Change-Id: Idfe0c97b216bb620cc7264e968b494eb3a765157
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>