media: atomisp: Remove duplicate atomisp_[start|stop]_streaming() prototypes

atomisp_ioctl.h contains the atomisp_[start|stop]_streaming() function
prototypes 2 times. Drop one of the copies of the prototypes.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>