net/mlx4_en: Fix mixed PFC and Global pause user control requests

Global pause and PFC configuration should be mutually exclusive (i.e. only
one of them at most can be set). However, once PFC was turned off,
driver automatically turned Global pause on. This is a bug.

Fix the driver behaviour to turn off PFC/Global once the user turned the
other on.

This also fixed a weird behaviour that at a current time, the profile
had both PFC and global pause configuration turned on, which is
Hardware-wise impossible and caused returning false positive indication
to query tools.

In addition, fix error code when setting global pause or PFC to change
metadata only upon successful change.

Also, removed useless debug print.

Fixes: af7d5185 ("net/mlx4_en: Add DCB PFC support through CEE netlink commands")
Fixes: c27a02cd

 ("mlx4_en: Add driver for Mellanox ConnectX 10GbE NIC")
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>