arm64: dts: marvell: armada-37xx: Add SATA comphy into main armada-37xx.dtsi file

SATA on A3720 SOC can use only comphy2, so move this definition from board
specific DTS file armada-3720-espressobin.dtsi into main A3720 SOC file
armada-37xx.dtsi.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>