tty: serial: 8250: Merge duplicate conditions

This patch refactors a switch case statement by merging an if condition
in the default case into an identical condition right after the switch
statement.
This comes with a slight change in behaviour: If pci_netmos_9900_numports
returns 0, an additional warning is printed.

Signed-off-by: Anton Würfel <anton.wuerfel@fau.de>
Signed-off-by: Phillip Raffeck <phillip.raffeck@fau.de>
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-kernel@i4.cs.fau.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>