usr/include: openrisc: don't HDRTEST bpf_perf_event.h

Since openrisc does not support PERF_EVENTS, omit the HDRTEST of
bpf_perf_event.h for arch/openrisc/.

Fixes a build error:
usr/include/linux/bpf_perf_event.h:14:28: error: field 'regs' has incomplete type

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>