wl1251: cmd: remove redundant assignment

-ENOMEM has been used as a return value,it is not necessary to
assign it, and if kzalloc fail,not need free it,so just return
-ENOMEM when kzalloc fail.

Signed-off-by: wengjianfeng <wengjianfeng@yulong.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210203060306.2832-1-samirweng1979@163.com