serial: samsung: remove unused 'irq' parameter

This parameter is not used anywhere, so we can get rid of it.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>