ACPI: fix NULL pointer dereference

Commit 71f6428 ("ACPI: utils: Fix reference counting in
for_each_acpi_dev_match()") started doing "acpi_dev_put()" on a pointer
that was possibly NULL.  That fails miserably, because that helper
inline function is not set up to handle that case.

Just make acpi_dev_put() silently accept a NULL pointer, rather than
calling down to put_device() with an invalid offset off that NULL
pointer.

Link: https://lore.kernel.org/lkml/[email protected]/
Reported-and-tested-by: Jens Axboe <[email protected]>
Tested-by: Daniel Scally <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: torvalds

include/acpi/acpi_bus.h

@@ -720,7 +720,8 @@ static inline struct acpi_device *acpi_dev_get(struct acpi_device *adev)
 
 static inline void acpi_dev_put(struct acpi_device *adev)
 {
-	put_device(&adev->dev);
+	if (adev)
+		put_device(&adev->dev);
 }
 
 struct acpi_device *acpi_bus_get_acpi_device(acpi_handle handle);