drm/panel: mantix: Improve power on sequence timings

drm/panel: mantix: Improve power on sequence timings

FP8006P datasheet mentions:

> It is necessary to wait 15msec after releasing RESX before sending
> commands. Also Sleep Out command cannot be sent for 120 msec.

This hasn't been respected by the driver so far, which could interfere
with the LCD init code sequence performed by the controller. In some cases
this leads to VCOM voltage being set to a wrong value, causing "halo"
effects, temporary burn-in around the edges of the screen and degraded
image contrast.

T3 and T4 are counted from when VDDI is enabled. There's no need to add
them when we've already waited more than that in T2 and T2d.

While FT8006P datasheet does not mention a delay between exiting sleep
mode and turning the display on, code provided by the vendor uses 120ms
there and it happens to be the same value as required in newer datasheets
for newer controllers from the same family, so it seems appropriate to
use it here as well.

Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260105-mantix-halo-fixes-v1-2-1ebc9b195a34@puri.sm