[POWERPC] Turn on tigon3 support in maple_defconfig

I think that most people who use maple_defconfig are doing so for a JS21,
so it might make sense to turn Tigon3 support on by default.

Built and booted on a JS21.
Signed-off-by: Amos Waterland <apw@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/configs/maple_defconfig

@@ -474,7 +474,7 @@ CONFIG_E1000=y
 # CONFIG_SKY2 is not set
 # CONFIG_SK98LIN is not set
 # CONFIG_VIA_VELOCITY is not set
-# CONFIG_TIGON3 is not set
+CONFIG_TIGON3=y
 # CONFIG_BNX2 is not set
 # CONFIG_MV643XX_ETH is not set