Add support for Cortex-A57 erratum 826974 workaround

Change-Id: I45641551474f4c58c638aff8c42c0ab9a8ec78b4
diff --git a/include/lib/cpus/aarch64/cortex_a57.h b/include/lib/cpus/aarch64/cortex_a57.h
index c512129..7711e69 100644
--- a/include/lib/cpus/aarch64/cortex_a57.h
+++ b/include/lib/cpus/aarch64/cortex_a57.h
@@ -61,6 +61,7 @@
  ******************************************************************************/
 #define CPUACTLR_EL1			S3_1_C15_C2_0	/* Instruction def. */
 
+#define CPUACTLR_DIS_LOAD_PASS_DMB	(1 << 59)
 #define CPUACTLR_DIS_OVERREAD		(1 << 52)
 #define CPUACTLR_NO_ALLOC_WBWA		(1 << 49)
 #define CPUACTLR_DCC_AS_DCCI		(1 << 44)