adp-ag101p: add product into MAINTAINERS list

Add ADP-AG101P into MAINTAINERS list.
Add ADP-AG101P into boards.cfg.

Signed-off-by: Macpaul Lin <macpaul@andestech.com>
diff --git a/boards.cfg b/boards.cfg
index 8b7a03b..5304f80 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -346,6 +346,7 @@
 qi_lb60                      mips        xburst      qi_lb60             qi
 nios2-generic                nios2       nios2       nios2-generic       altera
 adp-ag101                    nds32       n1213       adp-ag101           AndesTech      ag101
+adp-ag101p                   nds32       n1213       adp-ag101p          AndesTech      ag101
 PCI5441                      nios2       nios2       pci5441             psyent
 PK1C20                       nios2       nios2       pk1c20              psyent
 EVB64260                     powerpc     74xx_7xx    evb64260            -              -           EVB64260