clk: ti: Add support for dm814x ADPLL

On dm814x we have 13 ADPLLs with 3 to 4 outputs on each. The
ADPLLs have several dividers and muxes controlled by a shared
control register for each PLL.

Note that for the clocks to work as device drivers for booting on
dm814x, this patch depends on "ARM: OMAP2+: Change core_initcall
levels to postcore_initcall" that has already been merged.

Also note that this patch does not implement clk_set_rate for the
PLL, that will be posted later on when available.

Cc: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>