Staging: rtlwifi: Remove unused variable and the code

Remove unused variable and also remove unused code
associated with initializing the unused variable.

Unused variable was detected using the following
semantic patch by coccinelle.

@@
type T;
identifier i;
constant C;
@@

(
extern T i;
|
- T i;
  <+... when != i
- i = C;
  ...+>
)

Signed-off-by: Shreeya Patel <shreeya.patel23498@gmail.com>