vmw_balloon: include asm/io.h

Fix a build error due to missing virt_to_phys()
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: f0a1bf29 ("vmw_balloon: fix inflation with batching")
Cc: stable@vger.kernel.org
Cc: Xavier Deguillard <xdeguillard@vmware.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/vmw_balloon.c

@@ -45,6 +45,7 @@
 #include <linux/seq_file.h>
 #include <linux/vmw_vmci_defs.h>
 #include <linux/vmw_vmci_api.h>
+#include <linux/io.h>
 #include <asm/hypervisor.h>
 
 MODULE_AUTHOR("VMware, Inc.");