accel/kvm: Adjust the note about the minimum required kernel version

Since commit 126e7f7 ("kvm: require KVM_CAP_IOEVENTFD and
KVM_CAP_IOEVENTFD_ANY_LENGTH") we require at least kernel 4.5 to
be able to use KVM. Adjust the upgrade_note accordingly.
While we're at it, remove the text about kvm-kmod and the
SourceForge URL since this is not actively maintained anymore.

Fixes: 126e7f7 ("kvm: require KVM_CAP_IOEVENTFD and KVM_CAP_IOEVENTFD_ANY_LENGTH")
Signed-off-by: Thomas Huth <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Michael Tokarev <[email protected]>
Signed-off-by: Michael Tokarev <[email protected]>
(cherry picked from commit f180e367fce44b336105a11a62edf9610b6b2a06)

Author: huth

accel/kvm/kvm-all.c

@@ -2556,8 +2556,7 @@ static int kvm_init(MachineState *ms)
 {
     MachineClass *mc = MACHINE_GET_CLASS(ms);
     static const char upgrade_note[] =
-        "Please upgrade to at least kernel 2.6.29 or recent kvm-kmod\n"
-        "(see http://sourceforge.net/projects/kvm).\n";
+        "Please upgrade to at least kernel 4.5.\n";
     const struct {
         const char *name;
         int num;