clk: meson-g12a: fix VPU clock parents

First two VPU clock parents are wrong, fix it here.

Fixes: 085a4ea9

 ("clk: meson: g12a: add peripheral clock controller")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lkml.kernel.org/r/20190313135503.3198-1-narmstrong@baylibre.com