perf probe: Use hexadecimal type by default if possible

Use hexadecimal type by default if it is available on current running
kernel.

This keeps the default behavior of perf probe after changing the output
format of 'u8/16/32/64' to unsigned decimal number.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Naohiro Aota <naohiro.aota@hgst.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/147151074685.12957.16415861010796255514.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>