hotfix: fields DLSCH_DCI and ULSCH_DCI of UE_TEMPLATE had wrong size

The old value was 6, it should be 8 because those fields are
casted to 'struct DCI0_5MHz_FDD' and the like and those have
a size multiple of 32 bits, that is 4 or 8 bytes as of today.

(MAX_DCI_SIZE_BITS is 45, all the shifts, muls and adds lead
to a value of 8 after this commit and 6 before.)

The problem manifested itself with a 20MHz eNB. Push the traffic,
after a while the DL harq process 0 is not used anymore.
This is because DLSCH_DCI is directly followed by nb_rb in
the structure UE_TEMPLATE and setting a value for harq process 7
did overwrite nb_rb[0], putting much too big values in there,
leading to the scheduler to always refuse to reschedule because
the required RBs are impossibly huge (I saw values of 32744, 16384,
and others).