md/raid1: fix memory leak in raid1_run() if no active rdev

When `raid1_set_limits()` fails or when the array has no active
`rdev`, the allocated memory for `conf` is not properly freed.

Add raid1_free() call to properly free the conf in error path.

Fixes: 799af947 ("md/raid1: don't free conf on raid0_run failure")
Signed-off-by: Zheng Qixing <zhengqixing@huawei.com>
Link: https://lore.kernel.org/linux-raid/20250215020137.3703757-1-zhengqixing@huaweicloud.com


Singed-off-by: Yu Kuai <yukuai3@huawei.com>