libbpf: Add ARC support to bpf_tracing.h

Add PT_REGS macros suitable for ARCompact and ARCv2.

Signed-off-by: Vladimir Isaev <isaev@synopsys.com>
Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20220408224442.599566-1-geomatsi@gmail.com