ENGR00142098 - EPDC fb: Fix slow mode transitions when powerdown delay disabled

ENGR00142098 - EPDC fb: Fix slow mode transitions when powerdown delay disabled

- When the powerdown delay is set to FB_POWERDOWN_DISABLE, the
mxc_epdc_fb_flush_updates() function does not execute correctly, always
resulting in a time out while waiting to receive a completion that signals
that all updates have completed.  This causes long delays when changing the FB
mode, since a mode change will always result in a call to
mxc_epdc_fb_flush_updates().

Fixed this bug by creating a new mxc_epdc_fb_data variable to track whether
all active updates have completed.  mxc_epdc_fb_flush_updates() now
keys off of this variable to determine whether to wait for all
active updates to complete.

Signed-off-by: Danny Nold <dannynold@freescale.com>