x86, perfcounters: prepare for fixed-mode PMCs

Impact: refactor the x86 code for fixed-mode PMCs

Extend the data structures and rename the existing facilities
to allow for a 'generic' versus 'fixed' counter distinction.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index d038450..984da54 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -14,6 +14,7 @@
 #define _LINUX_PERF_COUNTER_H
 
 #include <asm/atomic.h>
+#include <asm/perf_counter.h>
 
 #include <linux/list.h>
 #include <linux/mutex.h>