UBUNTU: SAUCE: drop lingering gmb() macro

CVE-2017-5715 (Spectre v2 Intel)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/x86/include/asm/barrier.h

@@ -24,9 +24,6 @@
 #define wmb()	asm volatile("sfence" ::: "memory")
 #endif
 
-#define gmb() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \
-				       "lfence", X86_FEATURE_LFENCE_RDTSC);
-
 #ifdef CONFIG_X86_PPRO_FENCE
 #define dma_rmb()	rmb()
 #else