Change #warning to FIXME for ns8390.c

This driver really needs to be rewritten.
It tries to build both ISA and PCI images,
and makes life diffifult for the build system
and rom-o-matic.net.  The warning was just a reminder
that it needs to be cleaned up and re-factored
to split the PCI and ISA drivers.

src/drivers/net/ns8390.c

 
 **************************************************************************/
 
-#warning "ns8390.c: FIXME: split ISA and PCI, clean up"
+/* #warning "ns8390.c: FIXME: split ISA and PCI, clean up" */
+
 #if 1