omapdss: HDMI: Clean up the header files

Keep only OMAP4 HDMI core block related structs and enums in ti_hdmi_4xxx_ip.h,
move the rest to ti_hdmi.h. This holds all library specific data which will be
shared between OMAP4 and OMAP5/DRA7x HDMI encoder drivers.

Move the duplicate register read/write/wait_for_bit_change functions in the hdmi
library files to ti_hdmi.h

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