Functions i2400m_report_tlv*() are only called from
i2400m_report_hook(), called in a workqueue by
i2400m_report_hook_work(). The scheduler checks for device readiness
before scheduling.

Added an extra check for readiness in i2400m_report_hook_work(), which
makes all the checks down the line redundant.

Obviously the device state could change in the middle, but error
handling would take care of that.
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>