ixgbe: add warning when max_vfs is out of range.

The max_vfs parameter has a limit of 63 and silently fails (adding 0 vfs) when
it is out of range. This patch adds a warning so that the user knows something
went wrong. Also, this patch moves the warning in ixgbe_enable_sriov() to where
max_vfs is checked, so that even an out of range value will show the deprecated
warning. Previously, an out of range parameter didn't even warn the user to use
the new sysfs interface instead.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>