x86/HVM: make hvm_find_io_handler() static

This reduces the chance of misuse - calling it must in particular
always be accompanied by calling the corresponding ->complete() hook.
Constify its parameter at once.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/intercept.c
+++ b/xen/arch/x86/hvm/intercept.c
@@ -210,7 +210,7 @@ int hvm_process_io_intercept(const struc
     return rc;
 }
 
-const struct hvm_io_handler *hvm_find_io_handler(ioreq_t *p)
+static const struct hvm_io_handler *hvm_find_io_handler(const ioreq_t *p)
 {
     struct domain *curr_d = current->domain;
     unsigned int i;
--- a/xen/include/asm-x86/hvm/io.h
+++ b/xen/include/asm-x86/hvm/io.h
@@ -97,8 +97,6 @@ struct hvm_io_ops {
 int hvm_process_io_intercept(const struct hvm_io_handler *handler,
                              ioreq_t *p);
 
-const struct hvm_io_handler *hvm_find_io_handler(ioreq_t *p);
-
 int hvm_io_intercept(ioreq_t *p);
 
 struct hvm_io_handler *hvm_next_io_handler(struct domain *d);