net: wan: framer: Simplify API framer_provider_simple_of_xlate() implementation

Simplify framer_provider_simple_of_xlate() implementation by API
class_find_device_by_of_node().

Also correct comments to mark its parameter @dev as unused instead of
@args in passing.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241213-net_fix-v2-1-6d06130d630f@quicinc.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>