drm/msm: rename hdmi symbols

Global symbols in the kernel should be prefixed by the name
of the subsystem and/or driver to avoid conflicts when all
code is built-in.

In this case, function names like 'hdmi_register' or 'hdmi_set_mode'
are way too generic for an MSM specific DRM driver, so I'm renaming
them all to msm_hdmi_* here.

I also rename a lot of the 'static' symbols along with the global
names for consistency, even though those are relatively harmless;
they might only be slightly confusing when they show up in
backtraces.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Clark <robdclark@gmail.com>