mvebu: fix support for Marvell 8040 MACCHIATOBin

mvebu: fix support for Marvell 8040 MACCHIATOBin

Between kernels 4.20 and 5.0, a new variant of this board has been
introduced ("Single Shot"), and the existing one has been renamed
with the appendix "Double Shot". [1]
This also adjusted the first compatible in the list:

marvell,armada8040-mcbin -> marvell,armada8040-mcbin-doubleshot

This patch updates the OpenWrt implementation of this device by
adjusting the relevant references to that compatible (i.e., our
board name).

To still provide support for 4.19 with our setup, this adds a
small patch to change the compatible there as well.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1f0bbe2700051886b954192b6c1751233fe0f52

Cc: Tomasz Maciej Nowak <tomek_n@o2.pl>
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Tomasz Maciej Nowak <tomek_n@o2.pl>