doc: gen_devicetree_rest: Fix glob to handle both .yaml and .yml
doc: gen_devicetree_rest: Fix glob to handle both .yaml and .yml

The glob search was only finding .yaml files, however we do have a
few .yml bindings that got missed.

Signed-off-by: Kumar Gala <383ef5577c6e1178b93f59ec8d0936f76d2a98c4@kernel.org>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr