DSS: Fixed compilation warnings at device.c:504

Warning: comparison of distinct pointer types lacks a cast
Changed clamp macro to clamp_t with __u32 type

Change-Id: I1ab6169a79e8dfdfb2e3b87147e225382a64248d
Signed-off-by: Ievgen Musiichuk <ievgen.musiichuk@ti.com>

Conflicts:
	drivers/video/omap2/dsscomp/device.c