media: dt-bindings: ak7375: Convert to DT schema

Convert DT bindings document for AKM AK7375 VCM to DT schema
format and add an example.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>