ARM: dts: sunxi: Rename sunxi-q8-common.dtsi sunxi-reference-design-tablet.dtsi

Rename sunxi-q8-common.dtsi to sunxi-reference-design-tablet.dtsi. This
is part of renaming all the sun?i-q8-common.dtsi files to
sun?i-reference-design-tablet.dtsi since most of the hw-config in there
is shared by all sunxi tablets.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>