serial8250-em: Emma Mobile UART driver V2

This is V2 of the Emma Mobile 8250 platform driver.

The hardware itself has according to the data sheet
up to 64 byte FIFOs but at this point we only make
use of the 16550 compatible mode.

To support this piece of hardware the common UART
registers need to be remapped, and the access size
differences need to be handled.

The DLL and DLM registers can due to offset collision
not be remapped easily, and because of that this
driver makes use of ->dl_read() and ->dl_write()
callbacks. This in turn requires a registration
function that takes 8250-specific paramenters.

Future potential enhancements include DT support,
early platform driver console and fine grained PM.

Signed-off-by: Magnus Damm <damm@opensource.se>
Acked-by: Alan Cox <alan@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>