perf tools: Fix ABI compatibility bug in print_event_desc()

This patches cleans up local variable types for msz and ret.
They need to be size_t and ssize_t respectively.

It also fixes a bug whereby perf would not read attr struct
with a different size than what it knows about.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: ravitillo@lbl.gov
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-18-git-send-email-eranian@google.com


Signed-off-by: Ingo Molnar <mingo@elte.hu>