serial: icom: fix casting warning

icom_port->uart_port.membase is (unsigned char __iomem *); thus,
casting (unsigned char __iomem *) is necessary to fix the
following warning. Also, local symbols are staticized.

drivers/tty/serial/icom.c:108:26: warning: symbol 'start_proc' was not declared. Should it be static?
drivers/tty/serial/icom.c:116:26: warning: symbol 'stop_proc' was not declared. Should it be static?
drivers/tty/serial/icom.c:123:25: warning: symbol 'int_mask_tbl' was not declared. Should it be static?
drivers/tty/serial/icom.c:1569:54: warning: incorrect type in assignment (different address spaces)
drivers/tty/serial/icom.c:1569:54:    expected unsigned char [noderef] <asn:2>*membase
drivers/tty/serial/icom.c:1569:54:    got char *<noident>
drivers/tty/serial/icom.c:1090:9: warning: cast truncates bits from constant value (ffffff7f becomes 7f)

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