e1000e: fix heap overflow in e1000_set_eeprom

Fix a possible heap overflow in e1000_set_eeprom function by adding
input validation for the requested length of the change in the EEPROM.
In addition, change the variable type from int to size_t for better
code practices and rearrange declarations to RCT.

Cc: stable@vger.kernel.org
Fixes: bc7f75fa ("[E1000E]: New pci-express e1000 driver (currently for ICH9 devices only)")
Co-developed-by: Mikael Wessel <post@mikaelkw.online>
Signed-off-by: Mikael Wessel <post@mikaelkw.online>
Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>