ARM: Hack out assembly barriers when on tegra124.

The tegra124 AVP uses ARMv4 which doesn't support the barrier assembly
instructions. Unfortunately we assume that we can (and should) use those
during the bootblock and things don't build. In place of a more robust long
term solution, we can just chop those out on boards with the tegra124. This
is only supposed to be a short term, stop gap solution.

BUG=None
TEST=Built for pit, nyan. Booted into the bootblock on nyan.
BRANCH=None

Change-Id: Ifd0bfd3f7e30df6b5bcb1222c070922b81136b03
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/171151
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
diff --git a/src/arch/armv7/include/arch/cache.h b/src/arch/armv7/include/arch/cache.h
index 1cd9958..437be83 100644
--- a/src/arch/armv7/include/arch/cache.h
+++ b/src/arch/armv7/include/arch/cache.h
@@ -32,6 +32,7 @@
 #ifndef ARMV7_CACHE_H
 #define ARMV7_CACHE_H
 
+#include <config.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -74,19 +75,25 @@
 /* data memory barrier */
 static inline void dmb(void)
 {
+#if !defined(CONFIG_SOC_NVIDIA_TEGRA124) || !defined(__BOOT_BLOCK__)
 	asm volatile ("dmb" : : : "memory");
+#endif
 }
 
 /* data sync barrier */
 static inline void dsb(void)
 {
+#if !defined(CONFIG_SOC_NVIDIA_TEGRA124) || !defined(__BOOT_BLOCK__)
 	asm volatile ("dsb" : : : "memory");
+#endif
 }
 
 /* instruction sync barrier */
 static inline void isb(void)
 {
+#if !defined(CONFIG_SOC_NVIDIA_TEGRA124) || !defined(__BOOT_BLOCK__)
 	asm volatile ("isb" : : : "memory");
+#endif
 }
 
 /*