Makefile: use find instead of shell globs

So Makefile works with /bin/sh that's not bash.
Reported-by: Fredrik Rinnestam <fredrik@crux.nu>
Signed-off-by: Kyle McMartin <kyle@kernel.org>

Makefile

@@ -8,6 +8,7 @@ all:
 install:
 	mkdir -p $(DESTDIR)$(FIRMWAREDIR)
 	cp -r * $(DESTDIR)$(FIRMWAREDIR)
-	rm -f $(DESTDIR)$(FIRMWAREDIR)/usbdux/*dux \
-		$(DESTDIR)$(FIRMWAREDIR)/*/*.asm
-	rm $(DESTDIR)$(FIRMWAREDIR)/{WHENCE,LICENSE.*,LICENCE.*}
+	find $(DESTDIR)$(FIRMWAREDIR)/usbdux \( -name '*dux' -type f -or \
+		-name '*.asm' \) -exec rm -- {} \;
+	find $(DESTDIR)$(FIRMWAREDIR) \( -name 'WHENCE' -or -name 'LICENSE.*' -or \
+		-name 'LICENCE.*' \) -exec rm -- {} \;