IMA: fix non-ANSI declaration of ima_check_policy()

ima_check_policy() has no parameters, so use the normal void
parameter convention to make it match the prototype in the header file
security/integrity/ima/ima.h

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>