ice: remove return value comment for ice_reset_all_vfs

Since commit fe99d1c0 ("ice: make ice_reset_all_vfs void"), the
ice_reset_all_vfs function has not returned anything. The function comment
still indicated it did. Fix this.

While here, also add a line to clarify the function resets all VFs at once
in response to hardware resets such as a PF reset.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>