staging: android: logger: Add a TODO

A comment about a pre-existing bug data structure definition is added.
This bug was evidently introduced by Xiong Zhou in the patch
bd471258 ("staging: android: logger: use kuid_t instead of uid_t")
where the code was changed to hide a valid build warning instead of
solving the bug that was identified by it.

Signed-off-by: Somya Anand <somyaanand214@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>