MAINTAINERS: update CZ.NIC's Turris information

Add all the files maintained by Turris team, not only for MOX, but also
for Omnia.  Change website.

Link: https://lkml.kernel.org/r/20210325171123.28093-1-kabel@kernel.org


Signed-off-by: Marek Behún <kabel@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>