[PATCH] nvmet-tcp: fix data digest calculation for multiple H2CData PDUs

[Sagi Grimberg]

>> transfer length, it works if host sends only one H2CData PDU per cmd, if
>> host sends multiple H2CData PDU per cmd then target reports data digest
>> error.
>>
>> This issue was fixed in commit fda871c0ba5d ("nvmet-tcp: fix receive data
>> digest calculation for multiple h2cdata PDUs").
>>
>> commit ed0691cf5514 ("nvmet-tcp: fix regression in data_digest
>> calculation") reverted the fix done in the above commit.
> 
> This simply seems to revert this revert again and not address the
> reason why it was reverted.

We no longer map/unmap per pdu, so the original issue addressed
in fda871c0ba5d should no longer exist.

This part is missing from the change log though.