dt-bindings: arm: mrvl: Add missing compatible strings

Add compatible strings for the boards we have in tree. At the same time,
fix the MMP3 compatible string: the preferred vendor name for Marvell is
"marvell", not "mrvl", and indeed "marvell,mmp3" has been actively used,
not "mrvl,mmp3".

Fixes: 95aecb71 ("dt-bindings: arm: mrvl: Document MMP3 compatible string")
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Rob Herring <robh@kernel.org>