perf, x86: Undo some some *_counter* -> *_event* renames

The big rename:

 cdd6c482 perf: Do the big rename: Performance Counters -> Performance Events

accidentally renamed some members of stucts that were named after
registers in the spec. To avoid confusion this patch reverts some
changes. The related specs are MSR descriptions in AMD's BKDGs and the
ARCHITECTURAL PERFORMANCE MONITORING section in the Intel 64 and IA-32
Architectures Software Developer's Manuals.

This patch does:

 $ sed -i -e 's:num_events:num_counters:g' \
   arch/x86/include/asm/perf_event.h \
   arch/x86/kernel/cpu/perf_event_amd.c \
   arch/x86/kernel/cpu/perf_event.c \
   arch/x86/kernel/cpu/perf_event_intel.c \
   arch/x86/kernel/cpu/perf_event_p6.c \
   arch/x86/kernel/cpu/perf_event_p4.c \
   arch/x86/oprofile/op_model_ppro.c

 $ sed -i -e 's:event_bits:cntval_bits:g' -e 's:event_mask:cntval_mask:g' \
   arch/x86/kernel/cpu/perf_event_amd.c \
   arch/x86/kernel/cpu/perf_event.c \
   arch/x86/kernel/cpu/perf_event_intel.c \
   arch/x86/kernel/cpu/perf_event_p6.c \
   arch/x86/kernel/cpu/perf_event_p4.c

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1269880612-25800-2-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>