Revert "Unsignify lengths and addresses in chip functions and structs"

- probe_timing was changed to unsigned although we use negative values
  for special cases
- some code was not changed along hence did no longer compile:
  * dediprog's read and write functions
  * linux_spi's read and write functions
- it introduced a number of new sign conversion warnings
  (http://paste.flashrom.org/view.php?id=832)

To be safe this patch reverts all changes made in r1448, a corrected
patch will follow later.

Thanks to idwer for pointing out the problem first!

Corresponding to flashrom svn r1450.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/82802ab.c b/82802ab.c
index 8f671c9..ff2f535 100644
--- a/82802ab.c
+++ b/82802ab.c
@@ -141,7 +141,7 @@
 }
 
 /* chunksize is 1 */
-int write_82802ab(struct flashchip *flash, uint8_t *src, unsigned int start, unsigned int len)
+int write_82802ab(struct flashchip *flash, uint8_t *src, int start, int len)
 {
 	int i;
 	chipaddr dst = flash->virtual_memory + start;