media: cx231xx: fix potential sign-extension overflow on large shift

Shifting the u8 value[3] by an int can lead to sign-extension
overflow. For example, if value[3] is 0xff and the shift is 24 then it
is promoted to int and then the top bit is sign-extended so that all
upper 32 bits are set.  Fix this by casting value[3] to a u32 before
the shift.

Detected by CoverityScan, CID#1016522 ("Unintended sign extension")

Fixes: e0d3bafd ("V4L/DVB (10954): Add cx231xx USB driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/cx231xx/cx231xx-video.c

@@ -1389,7 +1389,7 @@ int cx231xx_g_register(struct file *file, void *priv,
 		ret = cx231xx_read_ctrl_reg(dev, VRT_GET_REGISTER,
 				(u16)reg->reg, value, 4);
 		reg->val = value[0] | value[1] << 8 |
-			value[2] << 16 | value[3] << 24;
+			value[2] << 16 | (u32)value[3] << 24;
 		reg->size = 4;
 		break;
 	case 1:	/* AFE - read byte */