USB: musb: fix the nop registration for OMAP3EVM

OMAP3EVM uses ISP1504 phy which doesn't require any programming and
thus has to use NOP otg transceiver.

Cleanups being done:
	- Remove unwanted code in usb-musb.c file
	- Register NOP in OMAP3EVM board file using
	  usb_nop_xceiv_register().
	- Select NOP_USB_XCEIV for OMAP3EVM boards.
	- Don't enable TWL4030_USB in omap3_evm_defconfig

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: Eino-Ville Talvala <talvala@stanford.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>