media: v4l: fwnode: Call CSI2 bus csi2, not csi

The function to parse CSI2 bus parameters was called
v4l2_fwnode_endpoint_parse_csi_bus(), rename it as
v4l2_fwnode_endpoint_parse_csi2_bus() in anticipation of CSI1/CCP2
support.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Tested-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>