doc: ARM: Use the right function name

Trivial fix.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/doc/README.arm-caches b/doc/README.arm-caches
index f6a52e3..dbb6190 100644
--- a/doc/README.arm-caches
+++ b/doc/README.arm-caches
@@ -47,7 +47,7 @@
 - cleanup_before_linux() should flush the D-cache, invalidate I-cache, and
   disable MMU and caches.
 - The following sequence is advisable while disabling d-cache:
-  1. disable_dcache() - flushes and disables d-cache
+  1. dcache_disable() - flushes and disables d-cache
   2. invalidate_dcache_all() - invalid any entry that came to the cache
 	in the short period after the cache was flushed but before the
 	cache got disabled.