dt-bindings: ap80x: replace AP806 with AP80x

Rename the text file and update "AP806" into "AP806/AP807" where
relevant.

Signed-off-by: Ben Peled <bpeled@marvell.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>