e1000e: fix potential NVM corruption on ICH9 with 8K bank size

The bank offset was being incorrectly calculated on ICH9 parts with a bank
size of 8K (instead of the more common 4K bank) which would cause any NVM
writes to be done on the wrong address after switching from bank 1 to bank
0.  Additionally, assume we are meant to use bank 0 if a valid bank is not
detected, and remove the unnecessary acquisition of the SW/FW/HW semaphore
when writing to the shadow ram version of the NVM image.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>