e1000e: Make watchdog use delayed work

Use delayed work instead of timers to run the watchdog of the e1000e
driver.

Simplify the code with one less middle function.

Signed-off-by: Detlev Casanova <detlev.casanova@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>