hw/xen/xen-hvm: Reduce included headers

hw/xen/xen-hvm: Reduce included headers

Have "hw/xen/xen-hvm-common.h" include the bare minimal set
of headers. Adapt sources to avoid errors when refactoring
unrelated headers such:

  include/hw/xen/xen-hvm-common.h:71:5: error: unknown type name ‘xenevtchn_handle’
     71 |     xenevtchn_handle *xce_handle;
        |     ^~~~~~~~~~~~~~~~
  hw/xen/xen-hvm-common.c: In function ‘cpu_get_ioreq’:
  hw/xen/xen-hvm-common.c:227:13: error: implicit declaration of function ‘hw_error’
    227 |             hw_error("Fatal error while trying to get io event!\n");
        |             ^~~~~~~~
        |             herror
  hw/xen/xen-hvm-common.c: In function ‘handle_ioreq’:
  hw/xen/xen-hvm-common.c:446:34: error: ‘target_ulong’ undeclared (first use in this function)
    446 |             (req->size < sizeof (target_ulong))) {
        |                                  ^~~~~~~~~~~~
  hw/i386/xen/xen-hvm.c: In function ‘xen_add_to_physmap’:
  hw/i386/xen/xen-hvm.c:298:22: error: implicit declaration of function ‘xen_replace_cache_entry’
    298 |         uint8_t *p = xen_replace_cache_entry(phys_offset, start_addr, size);
        |                      ^~~~~~~~~~~~~~~~~~~~~~~
  hw/i386/xen/xen-hvm.c:314:9: error: implicit declaration of function 'error_report' is invalid in C99
    314 |    error_report("relocate_memory %lu pages from GFN %"HWADDR_PRIx
             ^~~~~~~~~~~~
  hw/i386/xen/xen-hvm.c: In function ‘xen_log_global_start’:
  hw/i386/xen/xen-hvm.c:465:9: error: implicit declaration of function ‘xen_enabled’
    465 |     if (xen_enabled()) {
        |         ^~~~~~~~~~~
  hw/i386/xen/xen-hvm.c: In function ‘regs_to_cpu’:
  hw/i386/xen/xen-hvm.c:487:5: error: unknown type name ‘X86CPU’
    487 |     X86CPU *cpu;
        |     ^~~~~~
  hw/i386/xen/xen-hvm.c:492:15: error: ‘R_EAX’ undeclared (first use in this function)
    492 |     env->regs[R_EAX] = req->data;
        |               ^~~~~
        |               REG_RAX

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Message-Id: <20250218162618.46167-6-philmd@linaro.org>