rdma: introduce qemu_file_mode_is_not_valid()

QEMUFileRDMA also has read and write modes. This function is now
shared to reduce code duplication.

Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Chegu Vinod <chegu_vinod@hp.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
Tested-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 8fab0dd..dd3fd51 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -80,6 +80,7 @@
  * The buffer should be available till it is sent asynchronously.
  */
 void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size);
+bool qemu_file_mode_is_not_valid(const char *mode);
 
 static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
 {