drivers:video: Add dcmi support to stm32l4

[adityaganeshcu2k]

Is your enhancement proposal related to a problem? Please describe.

Yes currently zephyr rtos does not support dcmi for stm32l4 based controllers or discovery kits

Describe the solution you'd like

I would like to add dcmi support to the dtsi file for stm32l4

Describe alternatives you've considered

As of now there are no alternatives for this because stm's native camera support is from dcmi which is an already supported protocol by zephyr rtos

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