arm: plat-orion: use void __iomem pointers for UART registration functions

The registration functions for UARTs now take void __iomem pointers,
so we remove the temporary "unsigned long" casts from the
mach-*/common.c files.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>