protobuf: core-x86: mark gregs with hex field option

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

protobuf/core-x86.proto

+import "opts.proto";
+
 message user_x86_regs_entry {
 	required uint64			r15		=  1;
 	required uint64			r14		=  2;
@@ -56,6 +58,6 @@ message user_x86_fpregs_entry {
 
 message thread_info_x86 {
 	required uint64			clear_tid_addr	= 1;
-	required user_x86_regs_entry	gpregs		= 2;
+	required user_x86_regs_entry	gpregs		= 2[(criu).hex = true];
 	required user_x86_fpregs_entry	fpregs		= 3;
 }