ext4: remove set but rewrite variables

In the ext4_dx_add_entry function, the at variable is assigned but will
reset just after “again:” label. So delete the unnecessary assignment.
this will not chang the logic.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Artem Blagodarenko <artem.blagodarenko@gmail.com>
Link: https://lore.kernel.org/r/1621493752-36890-1-git-send-email-tiantao6@hisilicon.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>