ARM: dts: stm32: Enable WiFi on AV96

ARM: dts: stm32: Enable WiFi on AV96

The WiFi/Bluetooth SDIO chip is attached to SDMMC3 on AV96, describe it
in DT to make it available. Remove WiFi LED and turn it into a regulator,
because it is a GPIO controlling the WL_REG_ON input of the WiFi chip.
The LED is just an indicator connected to the same line, but not the
primary function.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>