Changed the u-boot file name from u-boot.imx to u-boot-dtb.imx in the...

Changed the u-boot file name from u-boot.imx to u-boot-dtb.imx in the documentation for i.MX6 reference hardware setup

content/reference_hardware/imx6q_sabrelite_setup.md

@@ -105,7 +105,7 @@ a USB to microUSB cable.
   `uboot-`<version>`-installer-mx6qsabrelite.img.gz` to the SD card.  Images
   can be found under the `installer` directory of the relevant release on the
   [Apertis image download](https://images.apertis.org/) site.
-- Mount the `data` partition on the SD card and retrieve the `u-boot.imx` file
+- Mount the `data` partition on the SD card and retrieve the `u-boot-dtb.imx` file
   from `deb-binaries/usr/lib/u-boot/mx6qsabrelite/` and copy to the folder
   where the imx loader was cloned.
 - Unmount the SD card and insert the SD card into the full SD card slot on the
@@ -124,7 +124,7 @@ a USB to microUSB cable.
 
 <!-- end list -->
 
-    $ sudo ./imx_usb ./u-boot.imx
+    $ sudo ./imx_usb ./u-boot-dtb.imx
 
 - Board should boot U-Boot and program the flash using the image on the SD
   card.