serial: samsung: fix casting warning

port->membase is (unsigned char __iomem *), not (unsigned long *)
__set_bit() uses (unsigned long *) as the second argument.
Thus, casting (unsigned long *)(unsigned long) is necessary
to fix the following sparse warnings.

drivers/tty/serial/samsung.c:142:33: warning: cast removes address space of expression
drivers/tty/serial/samsung.c:161:33: warning: cast removes address space of expression
drivers/tty/serial/samsung.c:176:33: warning: cast removes address space of expression
drivers/tty/serial/samsung.c:526:40: warning: cast removes address space of expression

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>