percpu: fix percpu accessors to potentially !cpu_possible() cpus: pnpbios

Impact: CPU iterator bugfixes

Percpu areas are only allocated for possible cpus.  In general, you
shouldn't access random cpu's percpu areas.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Adam Belay <ambx1@neo.rr.com>

drivers/pnp/pnpbios/bioscalls.c

@@ -481,7 +481,7 @@ void pnpbios_calls_init(union pnp_bios_install_struct *header)
 
 	set_base(bad_bios_desc, __va((unsigned long)0x40 << 4));
 	_set_limit((char *)&bad_bios_desc, 4095 - (0x40 << 4));
-	for (i = 0; i < NR_CPUS; i++) {
+	for_each_possible_cpu(i) {
 		struct desc_struct *gdt = get_cpu_gdt_table(i);
 		if (!gdt)
 			continue;