arm64: traps: remove duplicate include statement

asm/exception.h is included more than once. Remove the one that isn't
necessary.
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Link: https://lore.kernel.org/r/1609139108-10819-1-git-send-email-tiantao6@hisilicon.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/traps.c

@@ -42,7 +42,6 @@
 #include <asm/smp.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
-#include <asm/exception.h>
 #include <asm/system_misc.h>
 #include <asm/sysreg.h>