u-boot: compile with -O2 on PowerPC

gcc on PowerPC is currently compiled with -Os optimization disabled so
we have to use -O2 on PowerPC instead.

Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-bsp/uboot/u-boot.inc

@@ -23,7 +23,12 @@ do_compile () {
 	unset CFLAGS
 	unset CPPFLAGS
 	oe_runmake ${UBOOT_MACHINE}
-	oe_runmake all
+	# -Os is disabled on PowerPC
+	if [ ${TARGET_ARCH} == "powerpc" ] ; then
+		oe_runmake OPTFLAGS=-O2 all
+	else
+		oe_runmake all
+	fi
 }
 
 do_deploy () {