Implemented a new algorithm for ldpc decoding.

> LDPC decoder algorithm implements iterative message-passing layered decoding. Algorithm involves exchanging the belief information among the variable nodes and check nodes.
>
> Input LLRs "l" provide intrinsic information. Extrinsic information "r" generated in check node is passed to variable nodes.
>
> Belief information is updated iteratively in two steps:
>
> 1. Variable-to-Check step: Variable nodes transmit their belief information to the connected check nodes.
> 2. Check-to-Variable step: Check nodes process the received information, update it, and send it back to the connected variable nodes.
>
> The offset min-sum algorithm is chosen for its computational efficiency and ease of implementation while maintaining reliable decoding performance.

**Note:** _This patch removes the parity_check, as the CRC check is performed which is mandatory._

BER rates with the new implementation are shown in the table below,

| n | bg | mod_type | rv | Eb/N0 | ber_before | ber_after |
|---|----|----------|----|-------|------------|-----------|
| 300 | 2 | QPSK | 0 | 1.0 | 0.217548 | 0.019789 |
| 396 | 1 | QPSK | 0 | 1.0 | 0.211515 | 0.027611 |
| 1400 | 2 | QPSK | 0 | 1.0 | 0.279014 | 0.008802 |
| 1848 | 1 | QPSK | 0 | 1.0 | 0.251669 | 0.017381 |
| 4400 | 2 | QPSK | 0 | 1.0 | 0.321063 | 0.002338 |
| 5808 | 1 | QPSK | 0 | 1.0 | 0.253866 | 0.008661 |
| 10400 | 2 | QPSK | 0 | 1.0 | 0.332846 | 0.000411 |
| 13728 | 1 | QPSK | 0 | 1.0 | 0.254120 | 0.004200 |