IMA: open all files O_LARGEFILE

If IMA tried to measure a file which was larger than 4G dentry_open would fail
with -EOVERFLOW since IMA wasn't passing O_LARGEFILE.  This patch passes
O_LARGEFILE to all IMA opens to avoid this problem.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>