at91: Switch to SD_BOOT / CONFIG_NAND_BOOT

The values CONFIG_SYS_USE_NANDFLASH and CONFIG_SYS_USE_MMC serve the
same purpose as CONFIG_SD_BOOT / CONFIG_NAND_BOOT so migrate to using
these switches instead as they're already in Kconfig.

Cc: Stelian Pop <stelian@popies.net>
Cc: Heiko Schocher <hs@denx.de>
Cc: Daniel Gorsulowski <daniel.gorsulowski@esd.eu>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/sama5d2_xplained_qspiflash_defconfig b/configs/sama5d2_xplained_qspiflash_defconfig
index 24b509d..c857841 100644
--- a/configs/sama5d2_xplained_qspiflash_defconfig
+++ b/configs/sama5d2_xplained_qspiflash_defconfig
@@ -26,8 +26,8 @@
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
 CONFIG_SYS_LOAD_ADDR=0x22000000
 CONFIG_FIT=y
-CONFIG_SYS_EXTRA_OPTIONS="SYS_USE_MMC"
 CONFIG_QSPI_BOOT=y
+CONFIG_SD_BOOT=y
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk root=/dev/mmcblk0p1 rw rootwait"