staging: vt6655: channel.h: Fix comment style of SPDX License Identifier

Fix the comment style of SPDX License Identifier for header file based
on License Identifier syntax.

Signed-off-by: Madhumitha Prabakaran <madhumithabiw@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>