USB: pl2303: clean up driver somewhat

Use u16 rather than __u16.
Fix multi-line comment style.
Remove some comments.
Remove unnecessary whitespace and add some where appropriate.
Drop DRIVER_DESC define.
Merge and simplify multi-line error message.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>