serial: 8250_ni: Remove duplicate mapping

UPF_IOREMAP is for serial core to map the resource on behalf of the
driver. No need to perform this explicitly in the driver.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Chaitanya Vadrevu <chaitanya.vadrevu@emerson.com>
Reviewed-by: Chaitanya Vadrevu <chaitanya.vadrevu@emerson.com>
Link: https://lore.kernel.org/r/20250321182119.454507-3-andriy.shevchenko@linux.intel.com


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