Add support for Atmel's AT25F series of SPI flash chips

This adds support for the following chips:
 - AT25F512, AT25F512A, AT25F512B
 - AT25F1024, AT25F1024A
 - AT25F2048
 - AT25F4096

Besides the definitions of the the chips in flashchips.c this includes
- a dedicated probing method (probe_spi_at25f)
- pretty printing methods (spi_prettyprint_status_register_at25f*), and
- unlocking methods (spi_disable_blockprotect_at25f*)

Corresponding to flashrom svn r1637.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/spi.h b/spi.h
index 1733fd3..297125e 100644
--- a/spi.h
+++ b/spi.h
@@ -30,10 +30,10 @@
 /* INSIZE may be 0x04 for some chips*/
 #define JEDEC_RDID_INSIZE	0x03
 
-/* AT25F512A has bit 3 as don't care bit in commands */
-#define AT25F512A_RDID		0x15	/* 0x15 or 0x1d */
-#define AT25F512A_RDID_OUTSIZE	0x01
-#define AT25F512A_RDID_INSIZE	0x02
+/* Some Atmel AT25F* models have bit 3 as don't care bit in commands */
+#define AT25F_RDID		0x15	/* 0x15 or 0x1d */
+#define AT25F_RDID_OUTSIZE	0x01
+#define AT25F_RDID_INSIZE	0x02
 
 /* Read Electronic Manufacturer Signature */
 #define JEDEC_REMS		0x90