serial: Add driver for LPC32xx High Speed UARTs

This patch adds a driver for the 3 High Speed UARTs of the LPC32xx SoC that
support up to 921600bps. These UARTs are different from the 4 "Standard" UARTs
of the LPC32xx.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>