sh: Remove unused variable

Removes this annoying warning:

arch/sh/kernel/traps.c: In function ‘nmi_trap_handler’:
arch/sh/kernel/traps.c:183:15: warning: unused variable ‘cpu’ [-Wunused-variable]
  183 |  unsigned int cpu = smp_processor_id();

Fixes: fe3f1d5d ("sh: Get rid of nmi_count()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210414170517.1205430-1-eric.dumazet@gmail.com

arch/sh/kernel/traps.c

@@ -180,7 +180,6 @@ static inline void arch_ftrace_nmi_exit(void) { }
 
 BUILD_TRAP_HANDLER(nmi)
 {
-	unsigned int cpu = smp_processor_id();
 	TRAP_HANDLER_DECL;
 
 	arch_ftrace_nmi_enter();