perf tools powerpc: Add support for extended register capability

Add extended regs to sample_reg_mask in the tool side to use with `-I?`
option. Perf tools side uses extended mask to display the platform
supported register names (with -I? option) to the user and also send
this mask to the kernel to capture the extended registers in each
sample. Hence decide the mask value based on the processor version.

Currently definitions for `mfspr`, `SPRN_PVR` are part of
`arch/powerpc/util/header.c`. Move this to a header file so that these
definitions can be re-used in other source files as well.

Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Reviewed-by: Kajol Jain <kjain@linux.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Reviewed--by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org> <mikey@neuling.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
[Decide extended mask at run time based on platform]
Signed-off-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>