8250_men_mcb: Read num ports from register data.

8250_men_mcb: Read num ports from register data.

The IP Core Z025 and Z057 have a register where the amount of UART
ports is specified. Such register is located at offset 0x40.

This patch fixes the way the UART ports is calculated by reading
the actual register. Additionally a refactor was needed to achieve
this so we can keep track of the UART line and its offset which
also improves the remove callback.

Co-developed-by: Jorge Sanjuan Garcia <jorge.sanjuangarcia@duagon.com>
Signed-off-by: Jorge Sanjuan Garcia <jorge.sanjuangarcia@duagon.com>
Signed-off-by: Javier Rodriguez <josejavier.rodriguez@duagon.com>
Link: https://lore.kernel.org/r/20230705131423.30552-3-josejavier.rodriguez@duagon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>