sb/intel/i82801jx/sata.c: Drop always-false is_mobile check

Also remove the meaningless `sata_traffic_monitor` devicetree option.
Function parameters will be removed in a reproducible follow-up.

Change-Id: I70cf1e06cc8ace504a22be9f9c4441e3070f9e29
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44336
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/intel/dg43gt/devicetree.cb

@@ -22,7 +22,6 @@ chip northbridge/intel/x4x		# Northbridge
 			# Set AHCI mode.
 			register "sata_port_map"	= "0x1f"
 			register "sata_clock_request"	= "0"
-			register "sata_traffic_monitor"	= "0"
 
 			# Enable PCIe ports 0,2,3 as slots.
 			register "pcie_slot_implemented" = "0xb"