cpufreq/ppc: Add missing #include <asm/smp.h>

If CONFIG_SMP=n, <linux/smp.h> does not include <asm/smp.h>, causing:

drivers/cpufreq/ppc-corenet-cpufreq.c: In function 'corenet_cpufreq_cpu_init':
drivers/cpufreq/ppc-corenet-cpufreq.c:173:3: error: implicit declaration of function 'get_hard_smp_processor_id' [-Werror=implicit-funcuresh E. Warrier" <warrier@linux.vnet.ibm.com>
X-Patchwork-Id: 443703
Message-Id: <54EE5989.7010800@linux.vnet.ibm.com>
To: linuxppc-dev@ozlabs.org
Date: Wed, 25 Feb 2015 17:23:53 -0600

Export __spin_yield so that the arch_spin_unlock() function can
be invoked from a module. This will be required for modules where
we want to take a lock that is also is acquired in hypervisor
real mode. Because we want to avoid running any lockdep code
(which may not be safe in real mode), this lock needs to be
an arch_spinlock_t instead of a normal spinlock.
Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/lib/locks.c

@@ -41,6 +41,7 @@ void __spin_yield(arch_spinlock_t *lock)
 	plpar_hcall_norets(H_CONFER,
 		get_hard_smp_processor_id(holder_cpu), yield_count);
 }
+EXPORT_SYMBOL_GPL(__spin_yield);
 
 /*
  * Waiting for a read lock or a write lock on a rwlock...