net: atlantic: make _get_sw_stats return count as return value

This patch changes aq_vec_get_sw_stats() to return count as a return
value (which was unused) instead of an out parameter.

Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>