Convert CONFIG_SDCARD et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SDCARD
   CONFIG_SPIFLASH

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/P2020RDB-PC_SPIFLASH_defconfig b/configs/P2020RDB-PC_SPIFLASH_defconfig
index 2f14d87..ec5effd 100644
--- a/configs/P2020RDB-PC_SPIFLASH_defconfig
+++ b/configs/P2020RDB-PC_SPIFLASH_defconfig
@@ -20,7 +20,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="SPIFLASH"
+CONFIG_SPIFLASH=y
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="setenv bootargs root=/dev/$bdev rw rootdelay=30 console=$consoledev,$baudrate $othbootargs;usb start;ext2load usb 0:1 $loadaddr /boot/$bootfile;ext2load usb 0:1 $fdtaddr /boot/$fdtfile;bootm $loadaddr - $fdtaddr"