powerpc: Export cacheable_memzero as its now used in a driver

The Freescale PowerPC specific gianfar driver (gig-e) uses
cacheable_memzero for performance reasons we need to export
the symbol to allow the driver to be built as a module.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/ppc_ksyms.c

@@ -165,6 +165,7 @@ EXPORT_SYMBOL(timer_interrupt);
 EXPORT_SYMBOL(irq_desc);
 EXPORT_SYMBOL(tb_ticks_per_jiffy);
 EXPORT_SYMBOL(cacheable_memcpy);
+EXPORT_SYMBOL(cacheable_memzero);
 #endif
 
 #ifdef CONFIG_PPC32