sh/cpu: Mark play_dead() __noreturn

play_dead() doesn't return.  Annotate it as such.  By extension this
also makes arch_cpu_idle_dead() noreturn.

Link: https://lore.kernel.org/r/03549a74fad9f73576d57e6fc0b5102322f9cff4.1676358308.git.jpoimboe@kernel.orgSigned-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

arch/sh/include/asm/smp-ops.h

@@ -24,7 +24,7 @@ static inline void plat_smp_setup(void)
 	mp_ops->smp_setup();
 }
 
-static inline void play_dead(void)
+static inline void __noreturn play_dead(void)
 {
 	mp_ops->play_dead();
 	BUG();
@@ -43,7 +43,7 @@ static inline void register_smp_ops(struct plat_smp_ops *ops)
 {
 }
 
-static inline void play_dead(void)
+static inline void __noreturn play_dead(void)
 {
 	BUG();
 }