Add support for Atmel AT26DF041

Wicked chip: No WRSR, no write enable command (but swallows our
default one without a problem), supports an auto-erasing page write
(but even without that page writes are recommended to write the
whole page i.e. operate on a completely erased page), mad
requirements on block refreshments if only partly written.

Found on my Intel D946GZIS and tested with my serprog in situ.
Using the page write by setting JEDEC_BYTE_PROGRAM to 0x11 and using
the spi_chip_write_256 command greatly improves performance and works
flawlessly.

Corresponding to flashrom svn r1616.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/flashchips.c b/flashchips.c
index 8558ac8..937abd3 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -1795,18 +1795,24 @@
 		.total_size	= 512,
 		.page_size	= 256,
 		/* does not support EWSR nor WREN and has no writable status register bits whatsoever */
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_spi_rdid,
 		.probe_timing	= TIMING_ZERO,
 		.block_erasers	=
 		{
 			{
+				.eraseblocks = { {256, 2048} },
+				.block_erase = spi_block_erase_81,
+			}, {
+				.eraseblocks = { {2 * 1024, 256} },
+				.block_erase = spi_block_erase_50,
+			}, {
 				.eraseblocks = { {4 * 1024, 128} },
 				.block_erase = spi_block_erase_20,
 			}
-		},
-		.write		= NULL /* Incompatible Page write */,
-		.read		= spi_chip_read,
+		}, /* Supports also an incompatible page write (of exactly 256 B) and an auto-erasing write. */
+		.write		= spi_chip_write_1,
+		.read		= spi_chip_read, /* Fast read (0x0B) supported */
 		.voltage	= {2700, 3600}, /* 3.0-3.6V for higher speed, 2.7-3.6V normal */
 	},