Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 14de043..7f828fe 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -49,8 +49,7 @@
 #define array_index_mask_nospec array_index_mask_nospec
 
 /* Prevent speculative execution past this barrier. */
-#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \
-					   "lfence", X86_FEATURE_LFENCE_RDTSC)
+#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
 
 #define dma_rmb()	barrier()
 #define dma_wmb()	barrier()
@@ -80,8 +79,8 @@
 })
 
 /* Atomic operations are already serializing on x86 */
-#define __smp_mb__before_atomic()	barrier()
-#define __smp_mb__after_atomic()	barrier()
+#define __smp_mb__before_atomic()	do { } while (0)
+#define __smp_mb__after_atomic()	do { } while (0)
 
 #include <asm-generic/barrier.h>