Add the module dependency on the mem(4) module. This will fix the module

failing to load on a kernel that has "nodevice mem" in the config. It will
now properly bring in the mem(4) module.

Submitted by:	antoine
Reviewed by:	imp
MFC after:	1 week

sys/dev/tdfx/tdfx_pci.c

@@ -823,4 +823,5 @@ static driver_t tdfx_driver = {
 
 /* Tell Mr. Kernel about us! */
 DRIVER_MODULE(tdfx, pci, tdfx_driver, tdfx_devclass, 0, 0);
+MODULE_DEPEND(tdfx, mem, 1, 1, 1);
 MODULE_VERSION(tdfx, 1);