arm, usb, davinci: make USBPHY_CTL register configurable

Define CONFIG_DV_USBPHY_CTL for setting the USB PHY control
register.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Remy Bohmer <linux@bohmer.net>
cc: Sandeep Paulraj <s-paulraj@ti.com>
cc: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>