monitor: Call mon_get_cpu() only once at hmp_gva2gpa()

hmp_gva2gpa() calls mon_get_cpu() twice, which is unnecessary.
Not an actual bug, but this is reported as a defect by Coverity
Scan (CID 1401346).
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20190510185620.15757-1-ehabkost@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

monitor.c

@@ -1685,8 +1685,7 @@ static void hmp_gva2gpa(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    gpa  = cpu_get_phys_page_attrs_debug(mon_get_cpu(),
-                                         addr & TARGET_PAGE_MASK, &attrs);
+    gpa  = cpu_get_phys_page_attrs_debug(cs, addr & TARGET_PAGE_MASK, &attrs);
     if (gpa == -1) {
         monitor_printf(mon, "Unmapped\n");
     } else {