Serial: EG20T: add PCH_UART driver

UART driver of Intel EG20T(Topcliff) PCH

Intel EG20T PCH is the platform controller hub that is going to be used in
Intel's general embedded platform. All IO peripherals in
Intel EG20T PCH are actually devices sitting on AMBA bus.
Intel EG20T PCH has UART I/F. Using this I/F, it is able to access system
devices connected to UART.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>