Add a new interface "mxs_lcd_panel_setup" to setup fb parameters and
specifies the LCDIF controller for multiple controllers of iMX6SX.
Pass fb parameters via "videomode" env remains work if the new interface
is not called before video initialization.

Modify LCDIF clock interface "mxs_set_lcdclk" to support multiple
LCDIF controllers on iMX6SX.

Signed-off-by: Ye.Li <B37916@freescale.com>
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
(cherry picked from commit d7f49b9378547c3a57b96bcdb907fc44616beb3d)
(cherry picked from commit e1343191b9de227c582847e7eeb5ce9238be0754)