usb: musb: drop a gigantic amount of ifdeferry

the MUSB IP is always OTG, so there's no point
in adding so many ifdefs on the code. Drop those
and always compile the driver for OTG support.

This also allows us to drop the useless "driver
mode" choice. For doing that, we need to make
musb depend on both Host and Peripheral side.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>