selftests/rseq: Remove useless assignment to cpu variable

stable inclusion
from stable-v5.10.129
commit 68e1232c6e931d671db9e949fafbe651b511e8a4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YNDQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68e1232c6e931d671db9e949fafbe651b511e8a4



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commit 930378d0 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>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>