media: staging: media: imx: remove unnecessary variable use

Use of variable vc_num is unnecessary here as it is used only once.
Instead, the value can directly be used in place of the variable.

Signed-off-by: Deepak R Varma <mh12gx2825@gmail.com>
Acked-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>