This fixes the following genboardscfg.py warnings:
---8<---
WARNING: no status for 'at91sam9g20ek_2mmc'
WARNING: no maintainers for 'at91sam9g20ek_2mmc'
--->8---
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
 F:     configs/at91sam9g20ek_dataflash_cs0_defconfig
 F:     configs/at91sam9g20ek_dataflash_cs1_defconfig
 F:     configs/at91sam9g20ek_mmc_defconfig
+F:     configs/at91sam9g20ek_2mmc_defconfig
 F:     configs/at91sam9g20ek_nandflash_defconfig
 F:     configs/at91sam9xeek_dataflash_cs0_defconfig
 F:     configs/at91sam9xeek_dataflash_cs1_defconfig