selftests/rseq: Remove useless assignment to cpu variable

commit 930378d056eac2c96407b02aafe4938d0ac9cc37 upstream.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220124171253.22072-4-mathieu.desnoyers@efficios.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>