ixgbevf: Commonize mailbox write/read

With changes to ixgbevf_write_msg_read_ack(), other functions are
performing the same operations done here; change those functions to
utilize ixgbevf_write_msg_read_ack().

Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>