ppc4xx: Add dcache_enable() for 440

dcache_enable() was missing for 440 and the patch
017e9b7925f74878d0e9475388cca9bda5ef9482 ["allow ports to override bootelf
"] behavior uses this function.

Note: Currently the cache handling functions like
d/icache_disable/enable() are NOP's on 440. This may be changed in the
future.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/cpu/ppc4xx/cache.S b/cpu/ppc4xx/cache.S
index 5124dec..ceb3ec0 100644
--- a/cpu/ppc4xx/cache.S
+++ b/cpu/ppc4xx/cache.S
@@ -166,9 +166,11 @@
 #ifdef CONFIG_440
 
        .globl  dcache_disable
+       .globl  dcache_enable
        .globl  icache_disable
        .globl  icache_enable
 dcache_disable:
+dcache_enable:
 icache_disable:
 icache_enable:
 	blr