mt7601u: Remove redundant initialization of variable ret

The variable ret is being initialized with a value that is never read,
it is assigned later on with a different value. The initialization is
redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211007234153.31222-1-colin.king@canonical.com