skl mainboards/dt: Drop SataSalpSupport setting if disabled

The attributes are initialized with 0 and thus setting them to 0 makes
them superfluous. Remove them.

Change-Id: Icb41f0a9baded01267410bd4c9458ab4bfb82b70
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83175
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marvin Evers <marvin.n.evers@gmail.com>

src/mainboard/system76/kbl-u/devicetree.cb

@@ -128,7 +128,6 @@ chip soc/intel/skylake
 		end
 		device ref thermal on end
 		device ref sata on
-			register "SataSalpSupport" = "0"
 			register "SataSpeedLimit" = "2"
 			register "SataPortsEnable" = "{
 				[0] = 1,