tty: serial: uartlite: Support probe deferral

Give uartlite a chance to be probed when IRQ controller will be finally
available and return potential -EPROBE_DEFER as-is. The condition "<="
has been changed to "<" to follow the recommendation in the header of
platform_get_irq().

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Link: https://lore.kernel.org/r/20201127101953.23700-1-alexander.sverdlin@nokia.com


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