scsi: ufs: introduce the capability for interrupt aggregation

UFS HCI (Host Controller Interface) allows the transfer requests
interrupts to be aggregated to generate the single interrupt but
this can impact the performance. Hence introduce the capability which
gives choice to use the interrupt aggregation capability or not.
By default interrupt aggregation capability is kept disabled.

Change-Id: I2a7e85a33f8208553576df327ddd2e183639af0a
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>