configs: sun7i: Fix to use emmc dts for OLinuXino_MICRO-eMMC

A20 OLinuXino Micro eMMC board has emmc with mmc2 slot
so use proper dts, sun7i-a20-olinuxino-micro-emmc.dts

Cc: Stefan Mavrodiev <stefan@olimex.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>