instance_count defines number of instances of data block and instance
itself is indexed from zero, which means first instance has number 0.
Therefore check for invalid instance should be non-strict inequality.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Darren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>