Staging: bcm: return -EFAULT on copy_to_user() failures

There were a number of places in the bcm_char_ioctl() which returned the
number of bytes remaining to be copied instead of returning -EFAULT.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>