package/mender: do not automatically select uboot tools if uboot is selected

Because uboot requires a set of unique patches for each board, the
upstream package developers are phasing out supporting uboot wherever
possible.  Instead, they recommend using Grub2 as a secondary
bootloader and using the mender-grubenv package.

Because the mender-grubenv file provides it's own fw_printenv script,
it is not possible to know if U-Boot's fw_printenv or mender-grubenv's
fw_printenv should be used.

As such, remove selecting uboot tools when uboot is selected, and
instead add a more comprehensive note in the help section about what
Mender requires for uboot and grub2-based systems, with a link to the
meta-mender github project for the base uboot patches, and a link to
the official documentation on manual uboot integration.

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/mender/Config.in

@@ -5,14 +5,34 @@ config BR2_PACKAGE_MENDER
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	select BR2_PACKAGE_OPENSSL
 	select BR2_PACKAGE_XZ
-	select BR2_PACKAGE_UBOOT_TOOLS if BR2_TARGET_UBOOT # runtime
-	select BR2_PACKAGE_UBOOT_TOOLS_FWPRINTENV if BR2_TARGET_UBOOT # runtime
 	help
 	  Mender is an open source over-the-air (OTA) software updater
 	  for embedded Linux devices. Mender comprises a client
 	  running at the embedded device, as well as a server that
 	  manages deployments across many devices.
 
+	  Notes:
+	  For systems using uboot as the bootloader:
+	    - uboot must have the mender uboot patches applied.
+	    - uboot-tools must be selected.
+	    - fw_printenv must be functional on the device.
+	  The Mender Uboot patches are at:
+	  https://github.com/mendersoftware/meta-mender/
+
+	  For more information on Manual U-Boot integration, see:
+	  https://docs.mender.io/2.6/system-updates-yocto-project/board-integration/bootloader-support/u-boot/manual-u-boot-integration
+
+	  For systems using Grub2 as the bootloader:
+	    - Mender depends on the mender-grubenv package.
+	    - The mender-grubenv package provides a fw_printenv script,
+	      which is not compatible with the uboot-tools fw_printenv
+	      script.
+
+	  The mender project recommends using uboot to load Grub2 as a
+	  secondary bootloader whenever possible. Using Grub2 as a
+	  secondary bootloader prevents users from porting the patches
+	  for uboot to each new device.
+
 	  https://github.com/mendersoftware/mender
 
 comment "mender needs a toolchain w/ threads"