docs/misra: add entry to exclude-list.json

x86/efi/check.c is not part of the final Xen binary, therefore
it doesn't need to conform to MISRA guidelines at the moment.

Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

docs/misra/exclude-list.json

@@ -93,6 +93,10 @@
             "rel_path": "arch/x86/x86_64/mmconf-fam10h.c",
             "comment": "Imported from Linux, ignore for now"
         },
+        {
+            "rel_path": "arch/x86/efi/check.c",
+            "comment": "The resulting code is not included in the final Xen binary, ignore for now"
+        },
         {
             "rel_path": "common/bitmap.c",
             "comment": "Imported from Linux, ignore for now"