usb: udc: lpc32xx: remove direct access to clock controller registers

usb: udc: lpc32xx: remove direct access to clock controller registers

Direct access to clock control registers can be safely removed, the
task of clock management is done by platform clock driver based on
common clock framework.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>