staging: vt6655: check for memory allocation failures

There are no null pointer checking on rd_info and td_info values which
are allocated by kzalloc. It has potential null pointer dereferencing
issues. Implement error handling code on device_init_rd*, device_init_td*
and vnt_start for the allocation failures.

Signed-off-by: Ji-Hun Kim <ji_hun.kim@samsung.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>