powerpc: Make boot_cpuid common between 32 and 64-bit

Move the definition to setup-common.c and set the init value
to -1 on both 32 and 64-bit (it was 0 on 64-bit).

Additionally add a check to prom.c to garantee that the init
value has been udpated after the DT scan.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/prom.c

@@ -747,6 +747,10 @@ void __init early_init_devtree(void *params)
 	 * (altivec support, boot CPU ID, ...)
 	 */
 	of_scan_flat_dt(early_init_dt_scan_cpus, NULL);
+	if (boot_cpuid < 0) {
+		printk("Failed to indentify boot CPU !\n");
+		BUG();
+	}
 
 #if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
 	/* We'll later wait for secondaries to check in; there are

arch/powerpc/kernel/setup-common.c

@@ -76,6 +76,9 @@ EXPORT_SYMBOL(ppc_md);
 struct machdep_calls *machine_id;
 EXPORT_SYMBOL(machine_id);
 
+int boot_cpuid = -1;
+EXPORT_SYMBOL_GPL(boot_cpuid);
+
 unsigned long klimit = (unsigned long) _end;
 
 char cmd_line[COMMAND_LINE_SIZE];

arch/powerpc/kernel/setup_32.c

@@ -44,8 +44,6 @@
 
 extern void bootx_init(unsigned long r4, unsigned long phys);
 
-int boot_cpuid = -1;
-EXPORT_SYMBOL_GPL(boot_cpuid);
 int boot_cpuid_phys;
 EXPORT_SYMBOL_GPL(boot_cpuid_phys);
 

arch/powerpc/kernel/setup_64.c

@@ -74,7 +74,6 @@
 #define DBG(fmt...)
 #endif
 
-int boot_cpuid = 0;
 int spinning_secondaries;
 u64 ppc64_pft_size;