powerpc: Use TIDR CPU feature to control TIDR allocation

Switch the use of TIDR on it's CPU feature, rather than assuming it
is available based on architecture.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/process.c

@@ -1151,7 +1151,7 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 			mtspr(SPRN_TAR, new_thread->tar);
 	}
 
-	if (cpu_has_feature(CPU_FTR_ARCH_300) &&
+	if (cpu_has_feature(CPU_FTR_P9_TIDR) &&
 	    old_thread->tidr != new_thread->tidr)
 		mtspr(SPRN_TIDR, new_thread->tidr);
 #endif
@@ -1553,7 +1553,7 @@ void clear_thread_tidr(struct task_struct *t)
 	if (!t->thread.tidr)
 		return;
 
-	if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
+	if (!cpu_has_feature(CPU_FTR_P9_TIDR)) {
 		WARN_ON_ONCE(1);
 		return;
 	}
@@ -1576,7 +1576,7 @@ int set_thread_tidr(struct task_struct *t)
 {
 	int rc;
 
-	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+	if (!cpu_has_feature(CPU_FTR_P9_TIDR))
 		return -EINVAL;
 
 	if (t != current)