dt-bindings: pm8941-misc: rename misc node name

The spmi-pmic bindings is now using usb-detect@ for this node, so adjust
the example to match.

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>