Staging: rtl8192u: Use __func__ instead of function name.

Current function name is accessed using __func__.
Use '%s and __func__' instead of a function name.

Problem found by checkpatch.

Signed-off-by: Shreeya Patel <shreeya.patel23498@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>