drm/amd/display: Fix disable_otg_wa logic

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Fix disable_otg_wa logic

[Why]
When switching to another HDMI mode, we are unnecesarilly
disabling/enabling FIFO causing both HPO and DIG registers to be set at
the same time when only HPO is supposed to be set.

This can lead to a system hang the next time we change refresh rates as
there are cases when we don't disable OTG/FIFO but FIFO is enabled when
it isn't supposed to be.

[How]
Removing the enable/disable FIFO entirely.