media: dt-bindings: media: i2c: Fix external clock frequency for OV5645

Commit "4adb0a04 media: ov5645: Supported external clock is 24MHz"
modified the external clock frequency to be 24MHz instead of the
23.88MHz in driver. Hence, modify the frequency value in binding.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>