USB: ehci-msm2: Add module parameter to activate driver for uicc card

On some platforms, host only port is used for connecting peripherals
like uicc card. Userspace will come to know uicc card insertion and
use sysfs interface to activate driver and binds driver. Hence fail
probe for uicc card till userspace activates this driver through
sysfs.

Userspace has to run following commands to activate driver:
    1. echo Y > /sys/module/ehci_msm2/parameters/uicc_card_present
    2. echo msm_ehci_host > /sys/bus/platform/mdrivers/msm_ehci_host/bind

Also external vbus is not required for uicc card and hence don't fail
probe if no external vbus.

CRs-Fixed: 616098
Change-Id: I821bb2cabf4b5ba46fef71ac48a7df0b7aa74bf6
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>