scsi: ufs: Refactor ufshcd_is_intr_aggr_allowed()

Simplify if-else statement to return statement and remove code related to
CONFIG_SCSI_UFS_DWC that is not in use.

Link: https://lore.kernel.org/r/1891546521.01624860001810.JavaMail.epsvc@epcpadp3


Cc: Joao Pinto <jpinto@synopsys.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Keoseong Park <keosung.park@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>