clients: Use ARRAY_LENGTH macro in weston-simple-im
clients: Use ARRAY_LENGTH macro in weston-simple-im

Signed-off-by: Bryce Harrington <bdb14cfc1ab8d24e13de84adc40b41ae60c13bd1@osg.samsung.com>
Reviewed-by: Yong Bakos <d0d6c2a9047d8c98cd8ce1e9b46eb851dcd10a82@humanoriented.com>

sir-murray/weston,sir-murray/weston