dt-bindings: mmci: add optional reset property

This patch adds a optional reset management.
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/mmci.txt

@@ -15,6 +15,7 @@ Required properties:
 Optional properties:
 - arm,primecell-periphid : contains the PrimeCell Peripheral ID, it overrides
                            the ID provided by the HW
+- resets                 : phandle to internal reset line.
 - vqmmc-supply           : phandle to the regulator device tree node, mentioned
                            as the VCCQ/VDD_IO supply in the eMMC/SD specs.
 - st,sig-dir-dat0        : bus signal direction pin used for DAT[0].