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 <wd@denx.de>
Cc: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Tested-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
diff --git a/drivers/net/e1000.c b/drivers/net/e1000.c
index c86bf0a..6eab7b2 100644
--- a/drivers/net/e1000.c
+++ b/drivers/net/e1000.c
@@ -884,6 +884,7 @@
 	}
 
 	/* Compute the checksum */
+	checksum = 0;
 	for (i = 0; i < EEPROM_CHECKSUM_REG; i++)
 		checksum += buf[i];
 	checksum = ((uint16_t)EEPROM_SUM) - checksum;