media: atomisp: Fix EMBEDDED_FUNCTION_NAME warning

Use the automatically defined __func__ macro instead of the function name,
so it stays correct when the function is renamed.

Link: https://lore.kernel.org/linux-media/20201214110156.6152-4-Philipp.Gerlesberger@fau.de


Co-developed-by: Andrey Khlopkov <ij72uhux@stud.informatik.uni-erlangen.de>
Signed-off-by: Andrey Khlopkov <ij72uhux@stud.informatik.uni-erlangen.de>
Signed-off-by: Philipp Gerlesberger <Philipp.Gerlesberger@fau.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>