lxd/instance/qemu: Restrict HyperV flags to 5.10+
lxd/instance/qemu: Restrict HyperV flags to 5.10+

QEMU crashes on MSR related errors with 5.4 kernels, 5.10 and higher all
seem fine, so let's test for that.

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

hallyn/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,lxc/lxd