[media] smiapp: re-use clamp_t instead of min(..., max(...))

clamp_t does the job to put a variable into the given range.
clamp_t -> clamp as agreed with Andy.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>