usb: gadget: set appropriate max_ratio while entering and exiting UMS

We need to use a lower value of max_ratio for UICC device when operating
in UMS mode because UMS mode imposes a timeout of 10s to respond with CSW.
We want to keep max_ratio as minimum as possible in USM mode and with
max_ratio as 1 we are meeting throughput numbers and no functional issues
are seen, hence setting max_ratio to 1 when in UMS and to its original
value when exiting UMS. Also set nofua = 1 when this feature is enabeled.

Change-Id: I8e6051cf8fd371f6fb128ae4928a318cabf3d8c5
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>