ARM: dts: imx6sx-sabreauto: Fix misspelled property

In commit 99fc5ba0 ("ARM: dts: imx6sx: add i.mx6sx sabreauto board
support") it should've been enable-sdio-wakeup (not -wakup). But that is
now considered a legacy name for wakeup-source, so directly use the new
name instead, as done in commit 26cefdd1 for the other occurrence.

Fixes: 26cefdd1 ("ARM: dts: imx: replace legacy wakeup property with 'wakeup-source'")
Signed-off-by: Andreas Färber <afaerber@suse.de>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>