md: raid1: fix potential OOB in raid1_remove_disk()

If rddev->raid_disk is greater than mddev->raid_disks, there will be
an out-of-bounds in raid1_remove_disk(). We have already found
similar reports as follows:

1) commit d17f744e ("md-raid10: fix KASAN warning")
2) commit 1ebc2cec

 ("dm raid: fix KASAN warning in raid5_remove_disk")

Fix this bug by checking whether the "number" variable is
valid.

Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/tencent_0D24426FAC6A21B69AC0C03CE4143A508F09@qq.com


Signed-off-by: Song Liu <song@kernel.org>