I have MicroSom i2ex with fuses configured to boot from SATA. I have added support to u-boot (based on version: 2017.05-rc1) to boot from SATA for HummingBoard Pro board.
Here is repository: u-boot-imx6



hg clone https://kkubacki@bitbucket.org/kkubacki/u-boot-imx6//kkubacki@bitbucket.org/kkubacki/u-boot-imx6
export ARCH=arm
export CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf-
make mx6cuboxi_defconfig

As result we get two files: SPL and u-boot.img. SPL file should be placed at address 0x00000400 at SATA device.

Copy SPL to SATA device e.g. sda:

dd if=SPL of=/dev/sda bs=512 seek=2

u-boot.img should be placed on first EXT4 partition on SATA device.