usb: core: hcd: add missing header dependencies

We get 1 warning when building kernel with W=1:
drivers/usb/core/hcd.c:2390:5: warning: no previous prototype for 'usb_bus_start_enum' [-Wmissing-prototypes]

In fact, these functions are declared in linux/usb/otg.h, so this patch
adds the missing header dependencies.

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>