doc: Add vendor prefix for Kieback & Peter GmbH

The 'kiebackpeter' entry has been added to vendor-prefixes.txt to indicate
products from Kieback & Peter GmbH.
Signed-off-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -182,6 +182,7 @@ karo	Ka-Ro electronics GmbH
 keithkoep	Keith & Koep GmbH
 keymile	Keymile GmbH
 khadas	Khadas
+kiebackpeter    Kieback & Peter GmbH
 kinetic Kinetic Technologies
 kingnovel	Kingnovel Technology Co., Ltd.
 kosagi	Sutajio Ko-Usagi PTE Ltd.