sh: Don't enable clockevents broadcasting on UP SH-X3 builds.

Fixes up compile errors with missing timer definitions. It's pointless to
have this enabled anyways if CONFIG_SMP=n.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/Kconfig

@@ -326,7 +326,7 @@ config CPU_SUBTYPE_SHX3
 	select ARCH_SPARSEMEM_ENABLE
 	select SYS_SUPPORTS_NUMA
 	select SYS_SUPPORTS_SMP
-	select GENERIC_CLOCKEVENTS_BROADCAST
+	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 
 # SH4AL-DSP Processor Support