clk: meson: Add support for parameters for specific PLLs

In recent Amlogic GXBB, GXL and GXM SoCs, the GP0 PLL needs some specific
parameters in order to initialize and lock correctly.

This patch adds an optional PARAM table used to initialize the PLL to a
default value with it's parameters in order to achieve to desired frequency.

The GP0 PLL in GXBB, GXL/GXM also needs some tweaks in the initialization
steps, and these are exposed along the PARAM table.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1490178747-14837-2-git-send-email-narmstrong@baylibre.com