clk: meson: factorise meson64 peripheral clock controller drivers

The function used to probe the peripheral clock controller of the arm64
amlogic SoCs is mostly the same. We now have 3 of those controllers so
it is time to factorize things a bit.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20190201145345.6795-5-jbrunet@baylibre.com