clk: meson-gxbb: Add GP0 PLL init parameters

Tha Amlogic GXBB SoC GP0 PLL needs some vendor provided parameters to be
initializated in the the GP0 control registers before configuring the rate
with the rate table provided parameters.

GXBB GP0 PLL tweaks are also selected to respect the vendor init procedure.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1490178747-14837-3-git-send-email-narmstrong@baylibre.com