arm: socfpga: spl: Add support for booting from SD/MMC

Add code and configuration options to support booting from RAW
SD/MMC card as well as for ext4/vfat filesystems. Enable support
for booting from SD/MMC card, but don't enable the filesystem
support just yet to retain compatibility with old SoCFPGA card
format.

Signed-off-by: Marek Vasut <marex@denx.de>
5 files changed