arm: socfpga: update MAINTAINERS' file for cyclone5_socdk and arria5_socdk

commit "arm: socfpga: rename socfpga_cyclone5 and socfpga_arria5 config files"
renames the configs files, so we should update the MAINTAINERS' entry. At
the same time, update the email for Dinh Nguyen.
Signed-off-by: NDinh Nguyen <dinguyen@opensource.altera.com>

board/altera/arria5-socdk/MAINTAINERS

 SOCFPGA BOARD
-M:	Dinh Nguyen <dinguyen@altera.com>
+M:	Dinh Nguyen <dinguyen@opensource.altera.com>
 M:	Chin-Liang See <clsee@altera.com>
 S:	Maintained
 F:	board/altera/arria5-socdk/
-F:	include/configs/socfpga_arria5.h
+F:	include/configs/socfpga_arria5_socdk.h
 F:	configs/socfpga_arria5_defconfig

board/altera/cyclone5-socdk/MAINTAINERS

 SOCFPGA BOARD
-M:	Dinh Nguyen <dinguyen@altera.com>
+M:	Dinh Nguyen <dinguyen@opensource.altera.com>
 M:	Chin-Liang See <clsee@altera.com>
 S:	Maintained
 F:	board/altera/cyclone5-socdk/
-F:	include/configs/socfpga_cyclone5.h
+F:	include/configs/socfpga_cyclone5_socdk.h
 F:	configs/socfpga_cyclone5_defconfig
 
 SOCRATES BOARD