mlx5: minor fixes (mainly avoidance of hidden casts)

There were many places where parameters which should be u8/u16 were
integer type.

Additionally, in 2 places, a check for a non-null pointer was added
before dereferencing the pointer (this is actually a bug fix).

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
index 87d1b01..4671747 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
@@ -464,7 +464,7 @@
 	struct mlx5_cmd_msg *msg = input ? ent->in : ent->out;
 	struct mlx5_cmd_mailbox *next = msg->next;
 	int data_only;
-	int offset = 0;
+	u32 offset = 0;
 	int dump_len;
 
 	data_only = !!(mlx5_core_debug_mask & (1 << MLX5_CMD_DATA));