Synopsys: Cleanup files related to Synopsys

Add missing entries in DEVELOPERS file for synopsys boards.
Add missing readme.txt for recently introduced synopsys/hsdk board.
Reduce size of FAT partition for HSDK image.

Signed-off-by: Evgeniy Didin <didin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: arc-buildroot@synopsys.com
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

DEVELOPERS

@@ -163,7 +163,11 @@ F:	package/wf111/
 N:	ARC Maintainers <arc-buildroot@synopsys.com>
 F:	arch/Config.in.arc
 F:	board/synopsys/
+F:	configs/snps_arc700_axs101_defconfig
+F:	configs/snps_archs38_axs103_defconfig
+F:	configs/snps_archs38_haps_defconfig
 F:	configs/snps_archs38_hsdk_defconfig
+F:	configs/snps_archs38_vdk_defconfig
 
 N:	Ariel D'Alessandro <ariel@vanguardiasur.com.ar>
 F:	package/axfsutils/

board/synopsys/hsdk/genimage.cfg

@@ -7,7 +7,7 @@ image boot.vfat {
       image = "uboot-env.bin"
     }
   }
-  size = 100M
+  size = 20M
 }
 
 image sdcard.img {

board/synopsys/hsdk/readme.txt

@@ -0,0 +1,33 @@
+Synopsys, Inc.
+ARC HS Development Kit (HSDK)
+
+https://embarc.org/platforms.html
+
+How to build it
+===============
+
+Select the default configuration for the target:
+$ make snps_archs38_hsdk_defconfig
+
+Optional: modify the configuration:
+$ make menuconfig
+
+Build:
+$ make
+
+Result of the build
+===================
+output/images/
+├── boot.vfat
+├── rootfs.ext2
+├── sdcard.img
+├── u-boot
+├── u-boot.bin
+├── uboot-env.bin
+└── uImage
+
+To copy the image file to the sdcard use dd:
+$ dd if=output/images/sdcard.img of=/dev/XXX
+
+2018, Evgeniy Didin <Evgeniy.Didin@synopsys.com>
+