qemu: Use correct type when calling qemuPrepareNVRAM

qemuProcessStart was passing char * migrateFrom as the third argument to
qemuPrepareNVRAM. We should explicitly convert the pointer to bool which
is what the function expects.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_process.c

@@ -4428,7 +4428,7 @@ int qemuProcessStart(virConnectPtr conn,
      * Fill them in prior to setting the domain def as transient. */
     VIR_DEBUG("Generating paths");
 
-    if (qemuPrepareNVRAM(cfg, vm, migrateFrom) < 0)
+    if (qemuPrepareNVRAM(cfg, vm, !!migrateFrom) < 0)
         goto cleanup;
 
     /* Do this upfront, so any part of the startup process can add