nb/northbridge/intel/x4x/acpi.c: Remove variable set but not used

Change-Id: I715adbe3d90d0f5195b54c274fb7843945d3e6be
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32950
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/northbridge/intel/x4x/acpi.c

@@ -25,11 +25,9 @@
 
 unsigned long acpi_fill_mcfg(unsigned long current)
 {
-	struct device *dev;
 	u32 pciexbar = 0;
 	u32 length = 0;
 
-	dev = pcidev_on_root(0, 0);
 	if (!decode_pciebar(&pciexbar, &length))
 		return current;