sandbox: update documents regarding spi_sf

Since the commit 1289e96797bf ("sandbox: spi: Drop command-line SPI
option"), "--spi_sf" command line option is no longer supported.

So update the following documents to sync them up with the change.
	doc/arch/sandbox.rst
	doc/SPI/README.sandbox-spi

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/SPI/README.sandbox-spi b/doc/SPI/README.sandbox-spi
index dfa845c..f6a55fe 100644
--- a/doc/SPI/README.sandbox-spi
+++ b/doc/SPI/README.sandbox-spi
@@ -2,59 +2,37 @@
 ====================================
 
 U-Boot supports SPI and SPI flash emulation in sandbox. This must be enabled
-using the --spi_sf paramter when starting U-Boot.
+via a device tree.
 
 For example:
 
-$ make O=sandbox sandbox_config
-$ make O=sandbox
-$ ./sandbox/u-boot --spi_sf 0:0:W25Q128:b/chromeos_peach/out/image.bin
-
-The four parameters to spi_sf are:
-
-   SPI bus number (typically 0)
-   SPI chip select number (typically 0)
-   SPI chip to emulate
-   File containing emulated data
+	spi@0 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		reg = <0 1>;
+		compatible = "sandbox,spi";
+		cs-gpios = <0>, <&gpio_a 0>;
+		spi.bin@0 {
+			reg = <0>;
+			compatible = "spansion,m25p16", "jedec,spi-nor";
+			spi-max-frequency = <40000000>;
+			sandbox,filename = "spi.bin";
+		};
+	};
 
 Supported chips are W25Q16 (2MB), W25Q32 (4MB) and W25Q128 (16MB). Once
 U-Boot it started you can use 'sf' commands as normal. For example:
 
-$ ./b/sandbox/u-boot --spi_sf 0:0:W25Q128:b/chromeos_peach/out/image.bin \
-	-c "sf probe; sf test 0 100000; sf read 0 1000 1000; \
-		sf erase 1000 1000; sf write 0 1000 1000"
-
-
-U-Boot 2013.10-00237-gd4e0fdb (Nov 07 2013 - 20:08:15)
-
-DRAM:  128 MiB
-Using default environment
-
-In:    serial
-Out:   serial
-Err:   serial
-SF: Detected W25Q128BV with page size 256 Bytes, erase size 4 KiB, total 16 MiB
-SPI flash test:
-0 erase: 1 ticks, 1024000 KiB/s 8192.000 Mbps
-1 check: 2 ticks, 512000 KiB/s 4096.000 Mbps
-2 write: 6 ticks, 170666 KiB/s 1365.328 Mbps
-3 read: 0 ticks, 1048576000 KiB/s -201326.-592 Mbps
-Test passed
-0 erase: 1 ticks, 1024000 KiB/s 8192.000 Mbps
-1 check: 2 ticks, 512000 KiB/s 4096.000 Mbps
-2 write: 6 ticks, 170666 KiB/s 1365.328 Mbps
-3 read: 0 ticks, 1048576000 KiB/s -201326.-592 Mbps
-SF: 4096 bytes @ 0x1000 Read: OK
-SF: 4096 bytes @ 0x1000 Erased: OK
-SF: 4096 bytes @ 0x1000 Written: OK
-
+$ dd if=/dev/zero of=spi.bin bs=1M count=2
+$ u-boot -T
 
 Since the SPI bus is fully implemented as well as the SPI flash connected to
 it, you can also use low-level SPI commands to access the flash. For example
 this reads the device ID from the emulated chip:
 
 => sspi 0 32 9f
-FFEF4018
+SF: Detected m25p16 with page size 256 Bytes, erase size 64 KiB, total 2 MiB
+FF202015
 
 
 Simon Glass