Make cpu param to continue_hypercall_on_cpu() an unsigned integer.

Negative input makes no sense, and this makes the input range check
correct.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

xen/common/domain.c

@@ -943,7 +943,8 @@ static void continue_hypercall_tasklet_handler(unsigned long _info)
     }
 }
 
-int continue_hypercall_on_cpu(int cpu, long (*func)(void *data), void *data)
+int continue_hypercall_on_cpu(
+    unsigned int cpu, long (*func)(void *data), void *data)
 {
     struct migrate_info *info;
 

xen/include/xen/domain.h

@@ -64,7 +64,8 @@ bool_t domctl_lock_acquire(void);
 void domctl_lock_release(void);
 
 /* Continue the current hypercall via func(data) on specified cpu. */
-int continue_hypercall_on_cpu(int cpu, long (*func)(void *data), void *data);
+int continue_hypercall_on_cpu(
+    unsigned int cpu, long (*func)(void *data), void *data);
 
 extern unsigned int xen_processor_pmbits;