USB: MUSB: Add OMAP4 support in MUSB driver

This patch adds CONFIG_ARCH_OMAP4 macro within
MUSB driver.

Signed-off-by: Maulik Mankad <x0082077@ti.com>
Cc: David Brownell <david-b@pacbell.net>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: Olof Johansson <olof@lixom.net>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>