A number of style fixes across the files in this directory, including:

 * Correct invalid kernel-doc content.
 * Tidy up massive comment in fdt_region.c.
 * Use correct spelling of "U-Boot".
 * Replace tests of "! <var>" with "!<var>".
 * Replace "libfdt_env.h" with <libfdt_env.h>.
Signed-off-by: NRobert P. J. Day <rpjday@crashcourse.ca>
Acked-by: NSimon Glass <sjg@chromium.org>