net/mlx5: Fix return code in case of hyperv wrong size read

Return code value could be non deterministic in case of wrong size read.
With this patch, if such error occurs, set rc to be -EIO.

In addition, mlx5_hv_config_common() supports reading of
HV_CONFIG_BLOCK_SIZE_MAX bytes only, fix to early return error with
bad input.

Fixes: 913d14e8 ("net/mlx5: Add wrappers for HyperV PCIe operations")
Reported-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>