OMAP34xx: Enable USB in defconfig

This patch is for enabling USB support in the OMAP3430 defconfig
- enables the USBOTG by default
- enables EHCI USBHOST as a module
- enables SCSI support so that USBOTG and USBHOST can be tested with a mass storage device
- enables CONFIG_PM so that suspend/resume works for USBOTG and USBHOST

Changes tested on OMAP3430 SDP board with a mass storage device for USBOTG as well as USBHOST core.

Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>