OMAPDSS: HDMI: Remove HDMI PLL reset

The SYSRESET bits in HDMI PLL do not reset the PLL itself, but only
affect the power used for the PLL.

Afaik there is no reason to use the SYSRESET bits, and we don't use it
in the other PLLs, so let's remove the HDMI PLL reset to make the PLL
code simpler and similar to other PLLs.

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