tool/perf: Add sample_reg_mask to include all perf_regs

Add sample_reg_mask array with pt_regs registers.
This is needed for printing supported regs ( -I? option).

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>