runtime: Restore QEMUVIRTIOFSPATH variable in Makefile

Due to a bad edit / fixup in commit be6ee25, the variable
QEMUVIRTIOFSPATH was incorrectly removed from the makefile.

This problem was found by the 1.x CI checks, see
kata-containers/runtime#3005 (comment)

Fixes: #1017

Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>

src/runtime/Makefile

@@ -139,7 +139,8 @@ HYPERVISORS := $(HYPERVISOR_ACRN) $(HYPERVISOR_FC) $(HYPERVISOR_QEMU) $(HYPERVIS
 QEMUPATH := $(QEMUBINDIR)/$(QEMUCMD)
 QEMUVALIDHYPERVISORPATHS := [\"$(QEMUPATH)\"]
 
-QEMUVALIDVIRTIOFSPATHS := $(QEMUBINDIR)/$(QEMUVIRTIOFSCMD)
+QEMUVIRTIOFSPATH := $(QEMUBINDIR)/$(QEMUVIRTIOFSCMD)
+QEMUVALIDVIRTIOFSPATHS := [\"$(QEMUVIRTIOFSPATH)\"]
 
 CLHPATH := $(CLHBINDIR)/$(CLHCMD)
 CLHVALIDHYPERVISORPATHS := [\"$(CLHPATH)\"]