V4L/DVB (8906): v4l-dvb: fix assorted sparse warnings

Fix sparse warnings. None are serious, but cutting down on these helps find
future serious sparse warnings/errors.

Redid the av7710.c patch based on a suggestion by Oliver Endriss.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/em28xx/em28xx-i2c.c b/drivers/media/video/em28xx/em28xx-i2c.c
index 9785338..2989a65 100644
--- a/drivers/media/video/em28xx/em28xx-i2c.c
+++ b/drivers/media/video/em28xx/em28xx-i2c.c
@@ -143,10 +143,11 @@
 	}
 	for (write_timeout = EM2800_I2C_WRITE_TIMEOUT; write_timeout > 0;
 	     write_timeout -= 5) {
-		unsigned msg = dev->em28xx_read_reg(dev, 0x5);
-		if (msg == 0x94)
+		unsigned reg = dev->em28xx_read_reg(dev, 0x5);
+
+		if (reg == 0x94)
 			return -ENODEV;
-		else if (msg == 0x84)
+		else if (reg == 0x84)
 			return 0;
 		msleep(5);
 	}