USB-CDC: Fix coding style issues

Fixes most of checkpatch warnings and errors in USB gadget stack.

The most frequently encountered problems are:
1) "(foo*)", "foo * bar", "foo* bar"
2) C99 // comments
3) No spaces before/after/around '?', ':', '=', '==', ',', '&', '('
4) Spaces before '['
5) Spaces between function names and '('
6) Block braces in wrong places
7) Spaces before tabs
8) Macros with complex values not enclosed in parenthesis
9) Multiline comments start just after /*

Signed-off-by: Vitaly Kuzmichev <vkuzmichev@mvista.com>