Add 3 loads related dimension key wrappers.

They are to be displayed in the main cachelines overall output:

  ld_fbhit, ld_l1hit, ld_l2hit

They all display bare numbers of loads for
FB (Fill Buffer), L1 and L2 cache.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-wxrzhy74zl8fvkvgjae3w1ju@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>