staging: emxx_udc: Fix coding style errors

Only fixing errors reported by checkpatch.pl, based on the following
rules:
1. '*' should be adjacent to the data name or function name.
2. Don't use C99-style "// ..." comments.

Signed-off-by: KANG Yuxuan <stonekyx@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>