staging: bcm2835-audio: use min_t() macro instead of min()

use min_t() macro in place of min() to replace the two typecasts of min.
Change suggested by checkpatch script.

Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>