staging: r8188eu: Fixed a function declaration coding style issue

staging: r8188eu: Fixed a function declaration coding style issue

Added an identifier name for function definition argument
'struct timer_list *' as per checkpatch.pl

Note that for the same line checkpatch.pl will also complain "extern
should be avoided in .c". I am not very familiar with the codebase
so I decided not to move the declaration to a header file.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Chang Yu <marcus.yu.56@gmail.com>
Link: https://lore.kernel.org/r/778c21724752f2de136d82b31c9ffc2bf35ced55.1655872968.git.marcus.yu.56@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>