perf s390: add regs_query_register_offset()

The regs_query_register_offset() helper function converts
register name like "%r0" to an offset of a register in user_pt_regs
It is required by the BPF prologue generator.

The user_pt_regs structure was recently added to "asm/ptrace.h".
Hence, update tools/perf/check-headers.sh to keep the header file
in sync with kernel changes.

Suggested-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-and-tested-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>