drm/bridge: sii902x: re-order conditions to prevent out of bounds read

This should check that "i" is within bounds before checking reading from
the array.

Fixes: ff578163

 ("drm/bridge: sii902x: Implement HDMI audio support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607072704.GA25229@mwanda