generic: fix silicon labs spidev bindings

generic: fix silicon labs spidev bindings

Fix Silicon Labs bindings in the spidev driver

Some bindings for Silicon Labs chips already exists upstream.
These bindings can be found in trivial-devices.yaml.

The existing bindings are using "silabs" instead of "siliconlabs" to
identify the manufacturer.

This commit add two submitted patches for silabs chips and rename the
manufacturer in the different DTS for more coherence.

Signed-off-by: Vincent Tremblay <vincent@vtremblay.dev>