musb: Program extvbus for OMAP3EVM Rev >= E

OMAP3EVM Rev >=E uses external Vbus supply so setting 'extvbus'
to '1' for OMAP3EVM Rev >=E runtime based on EVM revision.

CC: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>