x86: convert dom_crash_sync_extable() annotation

... to that from the generic framework in xen/linkage.h.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/x86_64/entry.S

@@ -624,7 +624,7 @@ domain_crash_page_fault_0x8:
         ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
         movq  %rsi,%rdi
         call  show_page_walk
-ENTRY(dom_crash_sync_extable)
+LABEL(dom_crash_sync_extable, 0)
         ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
         # Get out of the guest-save area of the stack.
         GET_STACK_END(ax)