i40e/i40evf: Clean up a few things

1. There is no ixgbe_watchdog_task function in the driver, so change
   the comment to the correct function name, i40e_watchdog_subtask.
2. Remove num_msix_entries from interrupt set_up routine
   because it is never used.
3. Remove some TBD comments that are not needed.

Change-ID: I37697a04007074b797f85fd83d626672e4df1ad1
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>