[ARM] export __cpu_flush_dcache_page

Now required for libsas:

  Kernel: arch/arm/boot/Image is ready
  Kernel: arch/arm/boot/zImage is ready
  Building modules, stage 2.
  MODPOST 1096 modules
ERROR: "xscale_flush_kern_dcache_page" [drivers/scsi/libsas/libsas.ko] undefined!
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/proc-syms.c

@@ -27,6 +27,7 @@ EXPORT_SYMBOL(__cpuc_flush_kern_all);
 EXPORT_SYMBOL(__cpuc_flush_user_all);
 EXPORT_SYMBOL(__cpuc_flush_user_range);
 EXPORT_SYMBOL(__cpuc_coherent_kern_range);
+EXPORT_SYMBOL(__cpuc_flush_dcache_page);
 EXPORT_SYMBOL(dmac_inv_range);  /* because of flush_ioremap_region() */
 #else
 EXPORT_SYMBOL(cpu_cache);