dt-bindings: mfd: qcom-spmi-pmic: Document SMB2360 PMIC

Add bindings for SMB2360 PMIC. This PMIC is found in boards like
X1 Elite CRD and QCP.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20240527-smb2360-bindings-mfd-qcom-spmi-pmic-v1-1-31a2c051529c@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>