OMAPDSS: use DSI_FIFO_BUG workaround only for manual update displays

OMAPDSS: use DSI_FIFO_BUG workaround only for manual update displays

There is a problem related to DSS FIFO thresholds and power management
on OMAP3. It seems that when the full PM hits in, we get underflows. The
core reason is unknown, but after experiments it looks like only
particular FIFO thresholds work correctly.

This bug is related to an earlier patch, which added special FIFO
threshold configuration for OMAP3, because DSI command mode output
didn't work with the normal threshold configuration.

However, as the above work-around worked fine for other output types
also, we currently always configure thresholds in this special way on
OMAP3. In theory there should be negligible difference with this special
way and the standard way. The first paragraph explains what happens in
practice.

This patch changes the driver to use the special threshold configuration
only when the output is a manual update display on OMAP3. This does
include RFBI displays also, and although it hasn't been tested (no
boards using RFBI) I suspect the similar behaviour is present there
also, as the DISPC side should work similarly for DSI command mode and
RFBI.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Joe Woodward <jw@terrafix.co.uk>