modules/swcore: IB fix for double LL write when pck_err happens on the edge of mem pages

When pck_err occurred on the edge of two memory pages, status word with error
bit was written as the first word in the already used page. LL FSM was doing two
writes one after another with the same page addr, EOF and size 64 (first write)
and 1 (second write). Then if one of the Output Blocks was unlucky enough to
read LL between two writes, it was getting size = 64, while at the very
beginning of this page, status word was stored. This was making OB hang, not
freeing more pages and making the whole SWcore hang due to lack of free memory
pages.

LL FSM was writing twice
The fix is made of two parts:
 1. We must set mpm_dlast<='1' only for one cycle. If in_pck_eof happens right
    after in_pck_ere, then finish_rcv_pck is high for 2 cycles. When (as a
    result) mpm_dlast is high for 2 cycles, we go to unnecessary S_EOF_ON_WR in
    LL_FSM (on first mpm_dlast_d0 LL FSM goes to S_WRITE and if ll_wr_done_i
    does not come immediately after, we go to EOF_ON_WR).

2. If we got an error in received frame, RCV FSM stays in S_RCV_DATA for 2 last
   clock cycles and it was writing twice the last word into the MPM. This
   becomes a problem when ERR occurs at the edge of two pages. Then last word is
   written as 64-th word, then MPM requests next page, but does not get it and
   the same word is written to 1st position of the same page. The size for EOF
   is 64, and we end up having status word with error in the middle of our frame
   for Output Block. Thus we don't validate MPM write when we're for the 2nd
   time in S_RCV_DATA on pck_error.