mx7dsabresd: Add the qspi target to the list of supported defconfigs

Add an entry for mx7dsabresd_qspi_defconfig to avoid the following
warnings:

WARNING: no status info for 'mx7dsabresd_qspi'
WARNING: no maintainers for 'mx7dsabresd_qspi'
Reported-by: NTom Rini <trini@konsulko.com>
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>

board/freescale/mx7dsabresd/MAINTAINERS

@@ -4,3 +4,4 @@ S:	Maintained
 F:	board/freescale/mx7dsabresd
 F:	include/configs/mx7dsabresd.h
 F:	configs/mx7dsabresd_defconfig
+F:	configs/mx7dsabresd_qspi_defconfig