Added runtime programming for the differences in EHCI interface between
OMAP3EVM revisions (Rev >= E) and (Rev < E).

Changes:
	- EHCI PHY reset GPIO pin is 21 on Rev >= E while Rev < E
	  uses GPIO pin 135.
	- Rev >= E uses EHCI Vbus enable GPIO22 line.
	- Rev >= E uses GPIO61 to select EHCI port either on main board or
	  on Mistral Daughter Card (MDC). OMAP3EVM Rev < E doesn't have
	  EHCI port on main board.
	- Currently GPIO61 it programmed to enable EHCI port on main
	  board only.
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>