VMS: Add the missing -p32 and -p64 variants for x86_64

The pointer size support is already in the code, and is present for
all other supported hardwares.

Fixes #22899

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
(Merged from https://github.com/openssl/openssl/pull/23081)

(cherry picked from commit a43f253d58)

Configurations/10-main.conf

@@ -2125,5 +2125,15 @@ my %targets = (
         inherit_from     => [ "vms-generic" ],
         bn_ops           => "SIXTY_FOUR_BIT",
         pointer_size     => "",
+    },
+    "vms-x86_64-p32" => {
+        inherit_from     => [ "vms-x86_64" ],
+        cflags           => add("/POINTER_SIZE=32"),
+        pointer_size     => "32",
+    },
+    "vms-x86_64-p64" => {
+        inherit_from     => [ "vms-x86_64" ],
+        cflags           => add("/POINTER_SIZE=64=ARGV"),
+        pointer_size     => "64",
     }
 );