OMAP2PLUS: DSS2: DSI: Generalize DSI PLL Clock Naming

OMAP2PLUS: DSS2: DSI: Generalize DSI PLL Clock Naming

DSI PLL output clock names have been made more generic. The clock name
describes what the source of the clock and what clock is used for. Some of
DSI PLL parameters like dividers and DSI PLL source have also been made more
generic.

dsi1_pll_fclk and dsi2_pll_fclk have been changed as dsi_pll_hsdiv_dispc_clk
and dsi_pll_hsdiv_dsi_clk respectively. Also, the hsdividers are now named
regm_dispc and regm_dsi instead of regm3 and regm4.

Functions and macros named on the basis of these clock names have also been
made generic.

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