[PATCH] ARM64: dts: meson-gx: Use correct mmc clock source 0

Jerome Brunet [off-list ref] writes:

Now that the clock source 0 is properly described in the CCF, use it
instead of assuming the default value (xtal)

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---

This patchset depends on clock patchset adding the related clocks:
* https://lkml.kernel.org/r/20170731115603.29720-1-jbrunet at baylibre.com

I'll need a stable tag/commit in clk-meson/next/drivers to use in order
to apply this one.

Kevin