ice: Fix MAC address setting

Commit 2ccc1c1c ("ice: Remove excess error variables") merged
the usage of 'status' and 'err' variables into single one in
function ice_set_mac_address(). Unfortunately this causes
a regression when call of ice_fltr_add_mac() returns -EEXIST because
this return value does not indicate an error in this case but
value of 'err' remains to be -EEXIST till the end of the function
and is returned to caller.

Prior mentioned commit this does not happen because return value of
ice_fltr_add_mac() was stored to 'status' variable first and
if it was -EEXIST then 'err' remains to be zero.

Fix the problem by reset 'err' to zero when ice_fltr_add_mac()
returns -EEXIST.

Fixes: 2ccc1c1c

 ("ice: Remove excess error variables")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Alice Michael <alice.michael@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>