Convert SPI chips to partial write

However, wrap the write functions in a compat layer to allow converting
the rest of flashrom later. Tested on Intel NM10 by David Hendricks.

Corresponding to flashrom svn r1080.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Michael Karcher <flashrom@mkarcher.dialup.fu-berlin.de>
diff --git a/bitbang_spi.c b/bitbang_spi.c
index f60a7e1..adb1038 100644
--- a/bitbang_spi.c
+++ b/bitbang_spi.c
@@ -139,10 +139,8 @@
 	return spi_read_chunked(flash, buf, start, len, 64 * 1024);
 }
 
-int bitbang_spi_write_256(struct flashchip *flash, uint8_t *buf)
+int bitbang_spi_write_256(struct flashchip *flash, uint8_t *buf, int start, int len)
 {
-	int total_size = 1024 * flash->total_size;
-
-	msg_pdbg("total_size is %d\n", total_size);
-	return spi_write_chunked(flash, buf, 0, total_size, 256);
+	spi_disable_blockprotect();
+	return spi_write_chunked(flash, buf, start, len, 256);
 }