net: mvneta: eliminate wrong call to handle rx descriptor error

There are few reasons in mvneta_rx_swbm() function when received packet
is dropped. mvneta_rx_error() should be called only if error bit [16]
is set in rx descriptor.

[gregory.clement@free-electrons.com: add fixes tag]
Cc: stable@vger.kernel.org
Fixes: dc35a10f

 ("net: mvneta: bm: add support for hardware buffer management")
Signed-off-by: Yelena Krivosheev <yelena@marvell.com>
Tested-by: Dmitri Epshtein <dima@marvell.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>