powerpc: Show utsname->machine in boot-up banner

Currently we print "Starting Linux PPC64" at boot. But we don't mention
anywhere whether the kernel is big or little endian.

If we print the utsname->machine value instead we get either "ppc64" or
"ppc64le" which is much more informative, eg:

  Starting Linux ppc64le #1 SMP Wed Apr 15 12:12:20 AEST 2015
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/setup_64.c

@@ -523,7 +523,8 @@ void __init setup_system(void)
 	smp_release_cpus();
 #endif
 
-	pr_info("Starting Linux PPC64 %s\n", init_utsname()->version);
+	pr_info("Starting Linux %s %s\n", init_utsname()->machine,
+		 init_utsname()->version);
 
 	pr_info("-----------------------------------------------------\n");
 	pr_info("ppc64_pft_size    = 0x%llx\n", ppc64_pft_size);