intel_th: msu: Fix offset for wrapped block

Fix offset for the second pass on the wrapped block when iterating over
memory in multi-block mode, otherwise wrong part of the block will get
copied.

Signed-off-by: Laurent FERT <laurent.fert@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>