arm: only enable setend on ARMv6

Without this check it causes SIGILL crashes on ARMv5.
Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
(cherry picked from commit 5bf84a58)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/arm/cpu.c

@@ -128,7 +128,7 @@ int ff_get_cpu_flags_arm(void)
        trickle down. */
     if (flags & (AV_CPU_FLAG_VFPV3 | AV_CPU_FLAG_NEON))
         flags |= AV_CPU_FLAG_ARMV6T2;
-    else
+    else if (flags & (AV_CPU_FLAG_ARMV6T2 | AV_CPU_FLAG_ARMV6))
     /* Some functions use the 'setend' instruction which is deprecated on ARMv8
      * and serializing on some ARMv7 cores. This ensures such functions
      * are only enabled on ARMv6. */