Remove unneeded trailing slash from TOPDIR

Signed-off-by: Michael Roth <mroth@nessie.de>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

Makefile

@@ -22,7 +22,7 @@
 # Just run 'make menuconfig', configure stuff, then run 'make'.
 # You shouldn't need to mess with anything beyond this point...
 #--------------------------------------------------------------
-TOPDIR=./
+TOPDIR:=.
 CONFIG_CONFIG_IN=Config.in
 CONFIG_DEFCONFIG=.defconfig
 CONFIG=package/config