perf tools: Fix the bash completion for listing events of perf subcommand record|stat|top -e

The bash completion does not support listing events for 'perf kvm|kmem|
mem|lock|sched record|stat|top -e <TAB>', where 'kvm|kmem|mem|lock|sched'
are all subcommands of perf.

Example:

Before this patch:

 $ perf kvm record -e <TAB>
 $

As shown above, the events of record does not come out.

After this patch:

 $ perf kvm record -e <TAB>
 alignment-faults                   cpu/instructions/
 L1-dcache-prefetch-misses          node-prefetches
 uncore_rbox_0/qpi0_idle_filt/
 branch-instructions                cpu/mem-loads/
 L1-dcache-store-misses             node-prefetch-misses
 uncore_rbox_0/qpi1_date_response/
 branch-load-misses                 cpu-migrations
 L1-dcache-stores                   node-store-misses
 uncore_rbox_0/qpi1_filt_send/
 branch-loads                       dTLB-load-misses
 L1-icache-load-misses              node-stores
 uncore_rbox_0/qpi1_idle_filt/
 ...

As shown above, the events of record can come out now.

Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1426685758-25488-5-git-send-email-yunlong.song@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>