media: bcm2835-unicam: Fix driver path in MAINTAINERS

The MAINTAINERS file entry for the bcm2835-unicam driver incorrectly
references the non-existing drivers/media/platform/bcm2835/ path. Fix
it.

Fixes: 392cd78d

 ("media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface")
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Link: https://lore.kernel.org/r/20240501115439.9789-1-laurent.pinchart@ideasonboard.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>