media: rcar-dma: p_set can't be NULL

The only way for p_set to be NULL would be if vin_coef_set would be an
empty array.

On such case, the driver will OOPS, as it would try to de-reference a
NULL value. So, the check if p_set is not NULL doesn't make any sense.

Solves those two smatch warnings:

	drivers/media/platform/rcar-vin/rcar-dma.c:489 rvin_set_coeff() warn: variable dereferenced before check 'p_set' (see line 484)
	drivers/media/platform/rcar-vin/rcar-dma.c:494 rvin_set_coeff() error: we previously assumed 'p_set' could be null (see line 489)
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/rcar-vin/rcar-dma.c

@@ -486,7 +486,7 @@ static void rvin_set_coeff(struct rvin_dev *vin, unsigned short xs)
 	}
 
 	/* Use previous value if its XS value is closer */
-	if (p_prev_set && p_set &&
+	if (p_prev_set &&
 	    xs - p_prev_set->xs_value < p_set->xs_value - xs)
 		p_set = p_prev_set;