serial: exar: add CTI specific setup code

This is a large patch but is only additions. All changes and removals
are made in previous patches in this series.

- Add CTI board_init and port setup functions for each UART type
- Add CTI_EXAR_DEVICE() and CTI_PCI_DEVICE() macros
- Add support for reading a word from the Exar EEPROM.
- Add support for configuring and setting a single MPIO
- Add various helper functions for CTI boards.
- Add osc_freq to struct exar8250

Signed-off-by: Parker Newman <[email protected]>
Link: https://lore.kernel.org/r/ae4a66e7342b686cb8d4b15317585dfb37222cf4.1713382717.git.pnewman@connecttech.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: pnewman-cti