Bump buidlroot version to 2018.02.6

bsp/buildroot/package/powertop/0001-dont-force-stack-smashing-protection.patch

@@ -0,0 +1,18 @@
+Do not pass -fstack-protector unconditionally
+
+Using -fstack-protector only works when the toolchain has SSP support.
+
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+
+Index: b/src/Makefile.am
+===================================================================
+--- a/src/Makefile.am
++++ b/src/Makefile.am
+@@ -127,7 +127,6 @@
+ 	-Wformat \
+ 	-Wshadow \
+ 	-fno-omit-frame-pointer \
+-	-fstack-protector \
+ 	$(GLIB2_CFLAGS) \
+ 	$(LIBNL_CFLAGS) \
+ 	$(NCURSES_CFLAGS) \