media: MAINTAINERS: Add entry for STM32 DCMI media driver

Add an entry to make myself a maintainer of STM32 DCMI media driver.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>