fbdev: bf54x-lq043fb/bfin-t350mcqb-fb: drop custom mmap() handler

The common Blackfin code implements the get_fb_unmapped_area() function,
so we no longer need to have our own mmap() handler.  The common fb code
will take care of everything for us now.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>