omap3_beagle: enable EHCI and USB storage.

The reset sequence/configuration for ehci is highly board specific,
so this will be done in the source for the board, instead of
introducing several CONFIG_* which would be needed to make those
few lines in beagle.c usable across different OMAP boards.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>