gpu: ion: Fix incorrect BUG_ON()

ALIGN() -> IS_ALIGN().

Change-Id: I4451142932c5b33e83a8296c654226c41db73611
Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Reviewed-on: http://git-master/r/75530
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>