Disable split lock detection

We have experienced some cases where Guests are generating split lock
exceptions that are flooding the host kernel with traps causing a
tremendous impact to system's performance, besides flooding log buffers
with messages like the following:

x86/split lock detection: #AC: qemu-system-x86/4185 took a split_lock trap at address: 0x699e4dc1

There are several discussions about whether split lock detection should be
enabled or not. Since we cannot predict our workloads, let's disabled it to
avoid these situations.

Signed-off-by: Renê de Souza Pinto <[email protected]>

pkg/grub/rootfs.cfg

@@ -162,7 +162,7 @@ function set_generic {
 
    set_global dom0 /boot/kernel
    set_global dom0_rootfs "root=$rootfs_root"
-   set_global dom0_cmdline "$linuxkit_cmdline $panic_timeout rfkill.default_state=0"
+   set_global dom0_cmdline "$linuxkit_cmdline $panic_timeout rfkill.default_state=0 split_lock_detect=off"
 }
 
 function set_x86_64 {