MAINTAINERS: Add board/synopsys/

As of today 'board/synopsys/' folder contains only Synopsys ARC
boards supported by the same people who support 'arch/arc'.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 3209dcd..a054dc0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -60,6 +60,7 @@
 L:	uboot-snps-arc@synopsys.com
 T:	git git://git.denx.de/u-boot-arc.git
 F:	arch/arc/
+F:	board/synopsys/
 
 ARC HSDK CGU CLOCK
 M:	Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>