The musb support is enabled in omap3 platforms. For omap4 only board
support is available and the driver still isn't supported.
Because of this build with omap3_defconfig used for multi-omap
doesn't work on omap4430 sdp.

This patch avoids usb_musb_init() by adding a cpu check
in the board file.

Thanks to Anand Gadiyar and Mankad Maulik for the suggestion
of patching board file instead of musb driver.
Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>