drm/i2c: adv7511: Fix assignment of curr_mode

'curr_mode' in adv7511 struct is a pointer that's assigned to the
'adj_mode' pointer in mode_set. 'adj_mode' mode is later removed by
drm framework, causing 'curr_mode' pointing to an invalid mode.

Copy 'adj_mode' to 'curr_mode' in adv7511 to make sure we have the
correct 'curr_mode' with us all the time.

This fixes the issue of display not coming up after a blank/unblank
sequence.

Signed-off-by: Archit Taneja <architt@codeaurora.org>