ARM: dts: imx6q-prti6q: Fix ref/tcxo-clock-frequency properties

make dtbs_check gives the following errors:

ref-clock-frequency: size (9) error for type uint32
tcxo-clock-frequency: size (9) error for type uint32

Fix it by passing the frequencies inside < > as documented in
Documentation/devicetree/bindings/net/wireless/ti,wlcore.yaml.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Fixes: 0d446a50 ("ARM: dts: add Protonic PRTI6Q board")
Signed-off-by: Shawn Guo <shawnguo@kernel.org>