arm64: dts: meson: libretech-cc: set eMMC as removable

The eMMC on this board is add-on module which is not mandatory. Removing
'non-removable' property should prevent some errors when booting a board
w/o an eMMC module present.

Fixes: 72fb2c85 ("ARM64: dts: meson-gxl-s905x-libretech-cc: fixup board definition")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Martin <Blumenstingl&lt;martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>