[media] si2165: avoid division by zero

When si2165_init fails, the clk values in state are still at zero.
But the dvb-core ignores the return value of init will call tune
afterwards.
This will trigger a division by zero when tuning.
At least check for the variables to be non-zero before dividing.

This happened for a system with WinTV HVR-4400 PCIe-card after suspend-to-disk.
Do suspend-to-disk without accessing the DVB device before.
After wakeup try to tune.
si2165_init fails at checking the chip_mode and aborts.
Then si2165_set_if_freq_shift will fail with div-by-zero.
Signed-off-by: NMatthias Schwarzott <zzam@gentoo.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-frontends/si2165.c

@@ -751,6 +751,9 @@ static int si2165_set_oversamp(struct si2165_state *state, u32 dvb_rate)
 	u64 oversamp;
 	u32 reg_value;
 
+	if (!dvb_rate)
+		return -EINVAL;
+
 	oversamp = si2165_get_fe_clk(state);
 	oversamp <<= 23;
 	do_div(oversamp, dvb_rate);
@@ -775,6 +778,9 @@ static int si2165_set_if_freq_shift(struct si2165_state *state)
 		return -EINVAL;
 	}
 
+	if (!fe_clk)
+		return -EINVAL;
+
 	fe->ops.tuner_ops.get_if_frequency(fe, &IF);
 	if_freq_shift = IF;
 	if_freq_shift <<= 29;