powerpc/mpc85xx: work around erratum A-006593

Erratum A-006593 is "Atomic store may report failure but still allow
the store data to be visible".

The workaround is: "Set CoreNet Platform Cache register CPCHDBCR0 bit
21 to 1'b1.  This may have a small impact on synthetic write bandwidth
benchmarks but should have a negligible impact on real code."

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/arch/powerpc/cpu/mpc85xx/cmd_errata.c b/arch/powerpc/cpu/mpc85xx/cmd_errata.c
index 422782c..a7ed877 100644
--- a/arch/powerpc/cpu/mpc85xx/cmd_errata.c
+++ b/arch/powerpc/cpu/mpc85xx/cmd_errata.c
@@ -258,6 +258,9 @@
 #ifdef CONFIG_SYS_FSL_ERRATUM_USB14
 	puts("Work-around for Erratum USB14 enabled\n");
 #endif
+#ifdef CONFIG_SYS_FSL_ERRATUM_A006593
+	puts("Work-around for Erratum A006593 enabled\n");
+#endif
 	return 0;
 }