Drop unnecessary inclusions of pxa.h header

Seceral files contained onnecessary dependencies on hw/pxa.h header.
Drop unused references.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>

hw/tc6393xb.c

@@ -8,7 +8,6 @@
  * This code is licensed under the GNU GPL v2.
  */
 #include "hw.h"
-#include "pxa.h"
 #include "devices.h"
 #include "flash.h"
 #include "console.h"

hw/zaurus.c

@@ -16,7 +16,6 @@
  * with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 #include "hw.h"
-#include "pxa.h"
 #include "sharpsl.h"
 #include "sysbus.h"