kernel: x86_64: drop CALGARY IOMMU

The calgary IOMMU was only used on high-end IBM systems in the early
x86_64 age.  This is an unlikely OpenWrt target and in fact upstream
are looking to drop the driver entirely with the bonus that we no
longer see:

[ 0.000000] Calgary: detecting Calgary via BIOS EBDA area
[ 0.000000] Calgary: Unable to locate Rio Grande table in EBDA - bailing!

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>

target/linux/x86/64/config-4.19

@@ -75,8 +75,8 @@ CONFIG_NVME_MULTIPATH=y
 CONFIG_BLK_MQ_VIRTIO=y
 # CONFIG_BOOTPARAM_HOTPLUG_CPU0 is not set
 CONFIG_BTT=y
-CONFIG_CALGARY_IOMMU=y
-CONFIG_CALGARY_IOMMU_ENABLED_BY_DEFAULT=y
+# CONFIG_CALGARY_IOMMU=y
+# CONFIG_CALGARY_IOMMU_ENABLED_BY_DEFAULT=y
 CONFIG_CONNECTOR=y
 # CONFIG_CPU_HOTPLUG_STATE_CONTROL is not set
 CONFIG_CPU_RMAP=y