ENGR00178617 MX6x HDMI hotplug,video discontinuously after do a hotplug

ENGR00178617 MX6x HDMI hotplug,video discontinuously after do a hotplug

The issue only in play video on DP FG, no such issue on DP BG.
HDMI drvier will call fb_set_var to config framebuffer after HDMI cable plugin.
In Frame buffer driver, the DP FG and BG register as different fb.
The function fb_set_var only update one fb.
As IPU DP module, if DP BG is re-enabled, the FG should reconfig again.
So after HDMI plugin, only BG fb is update, FG fb will work incorrect,
no end of frame interrupt trigger, and print
"mxc_sdc_fb mxc_sdc_fb.0: timeout when waiting for flip irq"
to display.

Change code in function fb_set_var, FG fb will reconfig with DP BG fb.

Signed-off-by: Sandor Yu <R01008@freescale.com>