V4L/DVB (5840): fix dst and cx24123: tune() callback changed signess for delay

tune() dvb_frontend callback changed delay signess:
        int (*tune)(struct dvb_frontend* fe,
                    struct dvb_frontend_parameters* params,
                    unsigned int mode_flags,
-                   int *delay,
+                   unsigned int *delay,

This change caused warnings on cx24123 and dst modules:

/home/v4l/master/v4l/cx24123.c:1034: warning: initialization from incompatible pointer type
/home/v4l/master/v4l/dst.c:1782: warning: initialization from incompatible pointer type
/home/v4l/master/v4l/dst.c:1808: warning: initialization from incompatible pointer type
/home/v4l/master/v4l/dst.c:1837: warning: initialization from incompatible pointer type
/home/v4l/master/v4l/dst.c:1860: warning: initialization from incompatible pointer type

This patch corrects the function prototype on both modules to follow the
core change.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>