grub-module-verifier: Ignore all_video for xen_pvh

This solves the build failing with "Error: no symbol table and no
.moddeps section"

Also see:
- 6371e9c10433578bb236a8284ddb9ce9e201eb59
- https://savannah.gnu.org/bugs/?49012

Signed-off-by: Hans van Kranenburg <hans@knorrie.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>

util/grub-module-verifier.c

@@ -129,6 +129,7 @@ struct platform_whitelist {
 
 static struct platform_whitelist whitelists[] = {
   {"i386", "xen", (const char *[]) {"all_video", 0}},
+  {"i386", "xen_pvh", (const char *[]) {"all_video", 0}},
   {"x86_64", "xen", (const char *[]) {"all_video", 0}},
   {"sparc64", "ieee1275", (const char *[]) {"all_video", 0}},