omapdss: HDMI: create a PLL library

HDMI PLL is a block common to DSS in OMAP4, OMAP5 and DRA7x. Move the
existing PLL functions from ti_hdmi_4xxx_ip.c and hdmi.c to a separate file.
These funcs are called directly from the hdmi driver rather than hdmi_ip_ops
function pointer calls.

Add the PLL library function declarations to ti_hdmi.h. These will be shared
amongst the omap4/5 hdmi platform drivers. Remove the PLL function pointer ops
from the ti_hdmi_ip_ops struct. These will be shared amongst the omap4/5 hdmi
platform drivers and other libraries.

The DT/hwmod information for hdmi doesn't split the address space according to
the required sub blocks. Keep the address offset and size information in the
driver for now. This will be removed when the driver gets the information
correctly from DT/hwmod.

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