powerpc/cacheinfo: Set pr_fmt()

Set pr_fmt() so we get a nice prefix on messages.
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190627051537.7298-2-nathanl@linux.ibm.com

arch/powerpc/kernel/cacheinfo.c

@@ -7,6 +7,8 @@
  * Author: Nathan Lynch
  */
 
+#define pr_fmt(fmt) "cacheinfo: " fmt
+
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/kernel.h>