EHCI: HSIC: Pass interrupt threshold value as platform data

Interrupt threshold value is the maximum rate at which HSIC
controller will issue interrupts to processor. Increasing
this value results in fewer interrupts which may save power
as processor has to handle fewer interrupts. Side effect of
increasing this value is higher data latency. For fusion3,
set the ITC(interrupt threshold control) to 5 and default
for other targets. Also, allow ehci stack to set ITC value
per controller basis.

CRs-Fixed: 374661
Change-Id: I0e6bc210679ef211c2850ffbe1dfc80da2f65bf0
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>