x86/platform/goldfish: Prevent unconditional loading

The goldfish platform code registers the platform device unconditionally
which causes havoc in several ways if the goldfish_pdev_bus driver is
enabled:

 - Access to the hardcoded physical memory region, which is either not
   available or contains stuff which is completely unrelated.

 - Prevents that the interrupt of the serial port can be requested

 - In case of a spurious interrupt it goes into a infinite loop in the
   interrupt handler of the pdev_bus driver (which needs to be fixed
   seperately).

Add a 'goldfish' command line option to make the registration opt-in when
the platform is compiled in.

I'm seriously grumpy about this engineering trainwreck, which has seven
SOBs from Intel developers for 50 lines of code. And none of them figured
out that this is broken. Impressive fail!

Fixes: ddd70cf9 ("goldfish: platform device for x86")
Reported-by: NGabriel C <nix.or.die@gmail.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -1201,6 +1201,10 @@
 			When zero, profiling data is discarded and associated
 			debugfs files are removed at module unload time.
 
+	goldfish	[X86] Enable the goldfish android emulator platform.
+			Don't use this when you are not running on the
+			android emulator
+
 	gpt		[EFI] Forces disk with valid GPT signature but
 			invalid Protective MBR to be treated as GPT. If the
 			primary GPT is corrupted, it enables the backup/alternate

arch/x86/platform/goldfish/goldfish.c

@@ -42,10 +42,22 @@ static struct resource goldfish_pdev_bus_resources[] = {
 	}
 };
 
+static bool goldfish_enable __initdata;
+
+static int __init goldfish_setup(char *str)
+{
+	goldfish_enable = true;
+	return 0;
+}
+__setup("goldfish", goldfish_setup);
+
 static int __init goldfish_init(void)
 {
+	if (!goldfish_enable)
+		return -ENODEV;
+
 	platform_device_register_simple("goldfish_pdev_bus", -1,
-						goldfish_pdev_bus_resources, 2);
+					goldfish_pdev_bus_resources, 2);
 	return 0;
 }
 device_initcall(goldfish_init);