board/adp-ag102: add configuration of adp-ag102

board:
Add config file of board adp-ag102
Add adp-ag102 into boards.cfg
Add adp-ag102 into MAINTAINERS

doc:
add README of ag102

Signed-off-by: Macpaul Lin <macpaul@andestech.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 708ded7..e2441d8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1191,6 +1191,7 @@
 
 	ADP-AG101	N1213 (AG101 SoC)
 	ADP-AG101P	N1213 (AG101P XC5 FPGA)
+	ADP-AG102	N1213f (AG102 SoC with FPU)
 
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 # OpenRISC Systems:							#