8250_men_mcb: remove unnecessary cast when reading register

Fixes following sparse warning:

drivers/tty/serial/8250/8250_men_mcb.c:92:21: sparse: cast removes
    address space '__iomem' of expression
drivers/tty/serial/8250/8250_men_mcb.c:92:21: sparse: incorrect type
    in argument 1 (different address spaces) expected void const volatile
    [noderef] __iomem *addr got void *

Fixes: 2554e6ba ("8250_men_mcb: Read num ports from register data.")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307261517.x1O9OAkd-lkp@intel.com/


Signed-off-by: Jorge Sanjuan Garcia <jorge.sanjuangarcia@duagon.com>
Link: https://lore.kernel.org/r/20230803095816.110864-1-jorge.sanjuangarcia@duagon.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>