Fix alpha build failures

Don't include <asm/pci.h> in os-support/linux/lnx_axp.c, use "lnx.h" and
<unistd.h> instead

hw/xfree86/os-support/linux/lnx.h

@@ -11,7 +11,6 @@ extern int iopl __P ((int __level));
 
 /* new pciconfig_iobase syscall added in 2.2.15 and 2.3.99 */
 #  include <linux/unistd.h>
-#  include <asm/pci.h>
 extern long (*_iobase)(unsigned, int, int, int);
 
 /*

hw/xfree86/os-support/linux/lnx_axp.c

@@ -112,8 +112,8 @@ lnxGetAXP(void)
 /*
  * pciconfig_iobase wrappers and dynamic i/o selection
  */
-#include <linux/unistd.h>
-#include <asm/pci.h>
+#include "lnx.h"
+#include <unistd.h>
 #include <errno.h>
 
 /* glibc versions (single hose only) */