media: atmel: atmel-isc-base: replace is_streaming call in s_fmt_vid_cap

media: atmel: atmel-isc-base: replace is_streaming call in s_fmt_vid_cap

In s_fmt_vid_cap, we should check if vb2_is_busy and return EBUSY,
not check if it's streaming to return the busy state.

Suggested-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>