dmaengine: idma64: fix typo in WR_ISSUE_THD(x)

There is a typo in the definition of IDMA64C_CFGH_WR_ISSUE_THD(x). Fix it by
swapping characters.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>