sdhci-test: fix leaks

Fix the following ASAN reports:

==20125==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 24 byte(s) in 1 object(s) allocated from:
    #0 0x7f0faea03a38 in __interceptor_calloc (/lib64/libasan.so.4+0xdea38)
    #1 0x7f0fae450f75 in g_malloc0 ../glib/gmem.c:124
    #2 0x562fffd526fc in machine_start /home/elmarco/src/qemu/tests/sdhci-test.c:180

Indirect leak of 152 byte(s) in 1 object(s) allocated from:
    #0 0x7f0faea03850 in malloc (/lib64/libasan.so.4+0xde850)
    #1 0x7f0fae450f0c in g_malloc ../glib/gmem.c:94
    #2 0x562fffd5d21d in qpci_init_pc /home/elmarco/src/qemu/tests/libqos/pci-pc.c:122

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180215212552.26997-7-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/sdhci-test.c

@@ -209,8 +209,10 @@ static QSDHCI *machine_start(const struct sdhci_t *test)
 
 static void machine_stop(QSDHCI *s)
 {
+    qpci_free_pc(s->pci.bus);
     g_free(s->pci.dev);
     qtest_quit(global_qtest);
+    g_free(s);
 }
 
 static void test_machine(const void *data)