drivers:staging:ozwpan Replaced wrapper functions with actual spin lock function

* Replaced all the spin lock/unlock wrappers from oz_polling_lock_bh()
and oz_polllin_unlock_bh() with spin_lock_bh(&g_polling_lock) and
spin_unlock_bh(&g_polling_lock).Completely erased the wrappers defination
and declaration.
* declared g_polling_lock as global variable in header file and added comments to it.
Module builded successfully with sparse without warnings.

Signed-off-by: Surendra Patil <surendra.tux@gmail.com>
Acked-by: Rupesh Gujare <rupesh.gujare@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>