Unsignify lengths and addresses in chip functions and structs

Push those changes forward where needed to prevent new sign
conversion warnings where possible.

Corresponding to flashrom svn r1470.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
diff --git a/buspirate_spi.c b/buspirate_spi.c
index a556185..fd06b59 100644
--- a/buspirate_spi.c
+++ b/buspirate_spi.c
@@ -295,7 +295,8 @@
 		const unsigned char *writearr, unsigned char *readarr)
 {
 	static unsigned char *buf = NULL;
-	int i = 0, ret = 0;
+	unsigned int i = 0;
+	int ret = 0;
 
 	if (writecnt > 16 || readcnt > 16 || (readcnt + writecnt) > 16)
 		return SPI_INVALID_LENGTH;