Makefile: fix clean and install target

clean: do not try to wipe /usr/src/linux-...

load: rmmod and insmod do not have to be in /sbin (for example, /usr/bin
on Arch Linux). Assume that the user has a sane PATH.

Makefile

@@ -9,11 +9,11 @@ default:
 	$(MAKE) -C $(KDIR) M=$(PWD) modules
 
 clean:
-	$(MAKE) -C $(KDIR) M=$(PWD) clean
+	$(MAKE) O=$(PWD) -C $(KDIR) M=$(PWD) clean
 
 load:
-	-/sbin/rmmod $(modname)
+	-rmmod $(modname)
-	/sbin/insmod $(modname).ko
+	insmod $(modname).ko
 
 install:
 	mkdir -p /lib/modules/$(KVERSION)/misc/$(modname)