arm64: zynqmp: Add support for generic QSPI boot

arm64: zynqmp: Add support for generic QSPI boot

This patch is enabling support for SPL QSPI boot.

First of all it is necessary to generate atf-spi.ub which is different
format than atf-uboot.ub (this can be made as legacy image too)

ADDR=`arm-xilinx-linux-gnueabi-readelf -a bl31.elf | grep "Entry point
address" | cut -d ':' -f 2 | sed -e 's/^[ \t]*//'`
aarch64-linux-gnu-objcopy -O binary bl31.elf bl31.bin
./tools/mkimage -f auto -A arm64 -T firmware -C none -O u-boot -a $ADDR
-e $ADDR -n "atf1" -E -b arch/arm/dts/zynqmp-zcu102.dtb -d bl31.bin
atf-uboot.ub
./tools/mkimage -A arm64 -T firmware -C none -O u-boot -a $ADDR -e $ADDR
-n "atf-for-qspi" -E -d bl31.bin atf-spi.ub

This patch is using this QSPI layout with offsets:
0 boot.bin
512k atf-ub
640k u-boot.bin
1280k u-boot.img

Which corresponding by writing these images(read from MMC)
mmcinfo
sf probe
load mmc 0 10000000 boot.bin
sf erase 0 +$filesize
sf write 10000000 0 $filesize
load mmc 0 10000000 atf-spi.ub
sf erase 0x80000 +$filesize
sf write 10000000 0x80000 $filesize
load mmc 0 10000000 u-boot.bin
sf erase 0xa0000 +$filesize
sf write 10000000 0xa0000 $filesize
load mmc 0 10000000 u-boot.img
sf erase 0x140000 +$filesize
sf write 10000000 0x140000 $filesize

For testing u-boot running in EL3 you can break atf-spi.ub like this:
sf probe
sf erase 0x80000 +4

Then u-boot.img is executed.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>