hw/i386/sgx: Get rid of qemu_open_old()

For qemu_open_old(), osdep.h said:

> Don't introduce new usage of this function, prefer the following
> qemu_open/qemu_create that take an "Error **errp".

So replace qemu_open_old() with qemu_open(). And considering the SGX
enablement description is useful, convert it into a error message hint.

Cc: Paolo Bonzini <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Eduardo Habkost <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Marcel Apfelbaum <[email protected]>
Signed-off-by: Zhao Liu <[email protected]>
Reviewed-by: Michael Tokarev <[email protected]>
Signed-off-by: Michael Tokarev <[email protected]>

hw/i386/sgx.c

@@ -157,10 +157,12 @@ SGXInfo *qmp_query_sgx_capabilities(Error **errp)
 {
     SGXInfo *info = NULL;
     uint32_t eax, ebx, ecx, edx;
+    Error *local_err = NULL;
 
-    int fd = qemu_open_old("/dev/sgx_vepc", O_RDWR);
+    int fd = qemu_open("/dev/sgx_vepc", O_RDWR, &local_err);
     if (fd < 0) {
-        error_setg(errp, "SGX is not enabled in KVM");
+        error_append_hint(&local_err, "SGX is not enabled in KVM");
+        error_propagate(errp, local_err);
         return NULL;
     }