media: m5602_ov7660: remove the repeated declaration

Function 'ov7660_init' is declared twice, remove the repeated
declaration.

Cc: Erik Andren <erik.andren@gmail.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>