fbdev: sh_mobile_hdmi: fix regression: statically enable RTPM

A recent modification to the runtime PM code on mach-shmobile made a wrong
RTPM implementation in the sh_mobile_hdmi driver apparent, which broke
HDMI hotplug detection support on ap4evb. This patch does not implement a
proper dynamic RTPM support for sh_mobile_hdmi, instead it restores the
previous working state by statically enabling it. A more power-efficient
solution should be implemented for the next kernel version.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>