x86, bts: detect size of DS fields, fix

Impact: build fix

One usage site was missed in the sizeof_field -> sizeof_ptr_field
rename.

Cc: Markus Metzger <markus.t.metzger@intel.com>
LKML-Reference: <20090313104218.A30096@sedona.ch.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/ds.c

@@ -983,7 +983,7 @@ ds_configure(const struct ds_configuration *cfg,
 	printk("bts/pebs record: %u/%u bytes\n",
 	       ds_cfg.sizeof_rec[ds_bts], ds_cfg.sizeof_rec[ds_pebs]);
 
-	WARN_ON_ONCE(MAX_SIZEOF_DS < (12 * ds_cfg.sizeof_field));
+	WARN_ON_ONCE(MAX_SIZEOF_DS < (12 * ds_cfg.sizeof_ptr_field));
 }
 
 void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)