This decouples the TTY layer PORT_ types, which are exposed to
userspace, from the driver-internal flag of what kind of port this is.

This removes s3c24xx_serial_has_interrupt_mask, which was just checking
for a specific type anyway.
Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210304213902.83903-21-marcan@marcan.stSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>