staging: mei: updating mei driver documentation

The following changes were made in the document:

1. Update URLs to working links
2. remove old information about module parameters
3. Add IOCTL information.
4. cleanups and fix spelling
5. driver changed from character device to misc character device

Signed-off-by: Oren Weil <oren.jer.weil@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>