net: mvneta: fix bit assignment for RX packet irq enable

A value originally defined in the driver was inappropriate. Even though
the ingress was somehow working, writing MVNETA_RXQ_INTR_ENABLE_ALL_MASK
to MVNETA_INTR_ENABLE didn't make any effect, because the bits [31:16]
are reserved and read-only.

This commit updates MVNETA_RXQ_INTR_ENABLE_ALL_MASK to be compliant with
the controller's documentation.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>

Fixes: c5aff182 ("net: mvneta: driver for Marvell Armada 370/XP network
unit")
Signed-off-by: David S. Miller <davem@davemloft.net>