e1000: fix bugs from recent commits

e1000: fix bugs from recent commits

Commit 114d7fc0 "e1000: Rewrite EEPROM checksum error to give more
information" failed to initialize the checksum variable which should
result in random results. Fix that.

Commit 2326a94d caused a ton of "unused variable 'x'" warnings.
Fix these.  While we are at it, remove some bogus parens.

Signed-off-by: Wolfgang Denk <[email protected]>
Cc: Kyle Moffett <[email protected]>
Acked-by: Mike Frysinger <[email protected]>
Tested-by: Kyle Moffett <[email protected]>