ARM: davinci: usb: remove CONFIG_USB_MUSB_HOST etc

Remove usage of CONFIG_USB_MUSB_OTG, CONFIG_USB_MUSB_PERIPHERAL
and CONFIG_USB_MUSB_HOST in arch/arm/mach-davinci/usb.c since these
are not used anymore and set mode configuration by default to
MUSB_OTG.

Signed-off-by: Constantine Shulyupin <const@MakeLinux.com>
[prakash.pm@ti.com: Tested on DM6446-EVM]
Acked-by: Manjunathappa, Prakash <prakash.pm@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>