staging: wlan-ng: prism2mgmt.c: Drop void pointer cast

Void pointers don't need to be cast to other pointer types.
Semantic patch used:

@r@
expression x;
void* e;
type T;
identifier f;
@@

(
  *((T *)e)
|
  ((T *)x) [...]
|
  ((T *)x)->f
|
- (T *)
  e
)

Signed-off-by: Janani Ravichandran <janani.rvchndrn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>