dt-bindings: extcon: sm5502: Document siliconmitus,sm5504-muic

Document support for SM5504 with the new siliconmitus,sm5504-muic
compatible.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>