powerpc: Provide a suitable AT_PLATFORM value

The glibc folks want to use AT_PLATFORM to select between possible
alternative versions of shared libraries.  This commit makes the kernel
supply an AT_PLATFORM string that indicates what class of processor
we are running on.  Processors with the same set of user-level
instructions and roughly the same instruction scheduling characteristics
are given the same AT_PLATFORM value; for example, 821, 823 and 860
are all reported as "ppc823", and 7447, 7447A, 7448, 7450, 7451, 7455
are all called "ppc7450".

The intention is that the AT_PLATFORM values match the values that
gcc accepts for the -mcpu= option.  For values which are numeric
(e.g. -mcpu=750), "ppc" has been prepended.

This also adds a PPC_FEATURE_BOOKE bit to the AT_HWCAP value and sets
it for the 440 family and the Freescale 85xx family.

Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/cputable.h

@@ -19,6 +19,7 @@
 #define PPC_FEATURE_POWER5		0x00040000
 #define PPC_FEATURE_POWER5_PLUS		0x00020000
 #define PPC_FEATURE_CELL		0x00010000
+#define PPC_FEATURE_BOOKE		0x00008000
 
 #ifdef __KERNEL__
 #ifndef __ASSEMBLY__
@@ -64,6 +65,9 @@ struct cpu_spec {
 
 	/* Processor specific oprofile operations */
 	enum powerpc_oprofile_type oprofile_type;
+
+	/* Name of processor class, for the ELF AT_PLATFORM entry */
+	char		*platform;
 };
 
 extern struct cpu_spec		*cur_cpu_spec;