staging: android: ram_console: fix crash in ram_console_late_init

If the persistent ram buffer is not available, ram_console_late_init
would crash when dereferencing ram_console_zone.  Return early if
ram console was not initialized.

CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: NColin Cross <ccross@android.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ram_console.c

@@ -150,6 +150,9 @@ static int __init ram_console_late_init(void)
 	struct proc_dir_entry *entry;
 	struct persistent_ram_zone *prz = ram_console_zone;
 
+	if (!prz)
+		return 0;
+
 	if (persistent_ram_old_size(prz) == 0)
 		return 0;