arm64: dts: armada-3720-turris-mox: fix SFP binding

The sfp compatible should be 'sff,sfp', not 'sff,sfp+'. We used patched
kernel where the latter was working.

Fixes: 7109d817 ("arm64: dts: marvell: add DTS for Turris Mox")
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>