Add a COPYOPTS variable

The copy-firmware.sh script continues to grow new options and adding
bespoke make targets for them all isn't really sustainable.  This
introduces a COPYOPTS variable that can be set to pass arguments
directly to the script via a make invocation.  For now we just
include it on the 'install' target to preserve the existing behavior
of the rest.

Signed-off-by: Josh Boyer <jwboyer@kernel.org>

Makefile

@@ -28,7 +28,7 @@ rpm:
 
 install:
 	install -d $(DESTDIR)$(FIRMWAREDIR)
-	./copy-firmware.sh $(DESTDIR)$(FIRMWAREDIR)
+	./copy-firmware.sh $(COPYOPTS) $(DESTDIR)$(FIRMWAREDIR)
 
 install-nodedup:
 	install -d $(DESTDIR)$(FIRMWAREDIR)