firmware: turris-mox-rwtm: add marvell,armada-3700-rwtm-firmware compatible string

[ Upstream commit 90ae4721

 ]

Add more generic compatible string 'marvell,armada-3700-rwtm-firmware' for
this driver, since it can also be used on other Armada 3720 devices.

Current compatible string 'cznic,turris-mox-rwtm' is kept for backward
compatibility.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>