xen/apic/xenbus/swiotlb/pcifront/grant/tmem: Make functions or variables static.

There is no need for those functions/variables to be visible. Make them
static and also fix the compile warnings of this sort:

drivers/xen/<some file>.c: warning: symbol '<blah>' was not declared. Should it be static?

Some of them just require including the header file that
declares the functions.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/tmem.c

@@ -21,6 +21,7 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/page.h>
 #include <asm/xen/hypervisor.h>
+#include <xen/tmem.h>
 
 #define TMEM_CONTROL               0
 #define TMEM_NEW_POOL              1