doc: mkimage: Add SEE ALSO section

This adds a SEE ALSO section to link to similar man pages, as well as to
the U-Boot documentation.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/mkimage.1 b/doc/mkimage.1
index 6097876..bc28a5d 100644
--- a/doc/mkimage.1
+++ b/doc/mkimage.1
@@ -501,3 +501,11 @@
 This manual page was written by Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
 and Wolfgang Denk <wd@denx.de>. It was updated for image signing by
 Simon Glass <sjg@chromium.org>.
+.SH SEE ALSO
+.BR dtc (1),
+.BR dumpimage (1),
+.BR openssl (1),
+the\~
+.UR https://\:u-boot\:.readthedocs\:.io/\:en/\:latest/\:index.html
+U-Boot documentation
+.UE