Staging: rtl8192e: Fix declaration of symbols

Staging: rtl8192e: Fix declaration of symbols

The two declarations with issues in rtl_wx.h:

  * function: struct iw_statistics *r8192_get_wireless_stats();
  * variable: extern struct iw_handler_def r8192_wx_handlers_def;

The symbol 'r8192_get_wireless_stats' is declared as 'extern'
but it is only used in the local scope. The declaration is deleted
of rtl_wx.h, fixing the conflict with the 'extern' and 'static' scope.

The symbol 'r8192_wx_handlers_def' was fixed of some issues related
to variable declaration marked as 'extern' implicitly,
causing this sparse warning:

drivers/staging/rtl8192e/rtl8192e/rtl_wx.c:1323:24: warning: symbol
'r8192_wx_handlers_def' was not declared. Should it be static?

Resolved incluing the fixed header to rtl_wx.c

Also, isn't declared as constant variable, so it declared as such.
And delete unnecessary cast in rtl_core.c.

Signed-off-by: Joel Pelaez Jorge <joelpelaez@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>