When bus_setup fails in i2400m_post_reset(), it falls to the error path handler
"error_bus_setup:" which includes unlock the mutext. However, we didn't ever
try to the obtain the lock when running bus_setup.

The patch is to fix the misplaced error path handler "error_bus_setup:".
Signed-off-by: Cindy H Kao <cindy.h.kao@intel.com>