board: sl28: disable recovery watchdog

This board has an internal watchdog which supervises the board startup.
Although, the initial state of the watchdog is configurable, it is
enabled by default. In board_late_init(), which means almost everything
worked as expected, disable the watchdog.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/doc/board/kontron/sl28.rst b/doc/board/kontron/sl28.rst
index c2cdc5e..04483e1 100644
--- a/doc/board/kontron/sl28.rst
+++ b/doc/board/kontron/sl28.rst
@@ -23,17 +23,17 @@
 Install the bootloader on the board
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Please note, this bootloader doesn't support the builtin watchdog (yet),
-therefore you have to disable it, see below. Otherwise you'll end up in
-the failsafe bootloader on every reset::
+To install the bootloader binary use the following command::
 
  > tftp path/to/u-boot.rom
  > sf probe 0
  > sf update $fileaddr 0x210000 $filesize
 
-The board is fully failsafe, you can't break anything. But because you've
-disabled the builtin watchdog you might have to manually enter failsafe
-mode by asserting the ``FORCE_RECOV#`` line during board reset.
+The board is fully failsafe, you can't break anything. If builtin watchdog
+is enabled, you'll automatically end up in the failsafe bootloader if
+something goes wrong. If the watchdog is disabled, you have to manually
+enter failsafe mode by asserting the ``FORCE_RECOV#`` line during board
+reset.
 
 Update image
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