e1000e: Relax condition to trigger reset for ME workaround

It's an error if the value of the RX/TX tail descriptor does not match
what was written. The error condition is true regardless the duration
of the interference from ME. But the driver only performs the reset if
E1000_ICH_FWSM_PCIM2PCI_COUNT (2000) iterations of 50us delay have
transpired. The extra condition can lead to inconsistency between the
state of hardware as expected by the driver.

Fix this by dropping the check for number of delay iterations.

While at it, also make __ew32_prepare() static as it's not used
anywhere else.

CC: stable <stable@vger.kernel.org>
Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>