i2c: dev: Force case user pointers in compat_i2cdev_ioctl()

Sparse has warned us about wrong address space for user pointers:

  i2c-dev.c:561:50: warning: incorrect type in initializer (different address spaces)
  i2c-dev.c:561:50:    expected unsigned char [usertype] *buf
  i2c-dev.c:561:50:    got void [noderef] __user *

Force cast the pointer to (__u8 *) that is used by I²C core code.

Note, this is an additional fix to the previously addressed similar issue
in the I2C_RDWR case in the same function.

Fixes: 3265a7e6 ("i2c: dev: Add __user annotation")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/i2c-dev.c

@@ -557,7 +557,7 @@ static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned lo
 				.addr = umsg.addr,
 				.flags = umsg.flags,
 				.len = umsg.len,
-				.buf = compat_ptr(umsg.buf)
+				.buf = (__force __u8 *)compat_ptr(umsg.buf),
 			};
 		}