powerpc: Set CONFIG_32BIT on ppc32

commit ffe8018c of the -mm tree
fixes the initramfs size calculation for e.g. s390 but breaks it
for 32bit architectures which do not define CONFIG_32BIT.

This patch fix the problem for PPC32 which will elsewise end up
with a __initramfs_size of 0.
Signed-off-by: Kerstin Jonsson <kerstin.jonsson@ericsson.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -4,6 +4,10 @@ config PPC32
 	bool
 	default y if !PPC64
 
+config 32BIT
+	bool
+	default y if PPC32
+
 config 64BIT
 	bool
 	default y if PPC64