usb: musb: ux500: fix build warnings

This patch fixes the following build warnings:

drivers/usb/musb/ux500.c:346:12: warning: ‘ux500_suspend’ defined but
not used [-Wunused-function]
drivers/usb/musb/ux500.c:357:12: warning: ‘ux500_resume’ defined but not
used [-Wunused-function]

Signed-off-by: Felipe Balbi <balbi@ti.com>