Staging: vc04_services: remove unused variables

the volatile fields of bcm2835_alsa_stream -
control and status are not used.

$ grep bcm2835_alsa_stream
>From the above command all instances we see that
all variables of 'bcm2835_alsa_stream' are declared as
'alsa_stream'

So search for 'control' wherever we have 'alsa_stream'

$ grep -l 'alsa_stream' | xargs grep "control"
The above command returns where we don't any usage of
'control' field. which means that there is no usage of
these fields.

similarly for 'status' we see no usages.

Signed-off-by: Keerthi Reddy <keerthigd4990@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>