usb: cdns3: drd: simplify *switch_gadet and *switch_host

Patch split function cdns3_drd_switch_gadget and
cdns3_drd_switch_host into:
- cdns3_drd_host_on
- cdns3_drd_host_off
- cdns3_drd_gadget_on
- cdns3_drd_gadgett_off

These functions don't have any shared code so it's better to
have smaller, faster and easier functions.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>