Revert "OMAPDSS: APPLY: add fifo-merge support"

This reverts commit 1d71f42b.

Adding fifo merge feature as an omapdss internal configuration was a
mistake. We cannot hide from the users of omapdss the complexities of
fifo merge.

This commit removes the fifo merge support, which luckily is easily done
as it was handled totally inside apply.c. Note that this is not a 1:1
revert, but some resolving was needed for the dss_ovl_setup_fifo.

The plan is to try fifo merge again later when it is more clear how the
hardware acts in various situations, and how the omapdrm wants to use
fifo merge.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>