CMSIS-Driver: Minor update to vStream Driver API documentation (#238)

/**

\fn void *vStreamGetBlock (void)

\details

This function provides access to the current data block used for input or output operations,

This function provides access to the data block used for input or output operations,

depending on the streaming direction.

- For input streams (receiving data): returns a pointer to the oldest unread data block.  

/**

\fn int32_t vStreamReleaseBlock (void)

\details

This function finalizes the use of the current data block returned by \ref vStreamGetBlock.

This function finalizes the use of the data block returned by \ref vStreamGetBlock.

- For input streams: marks the block as processed, making it available for reuse by the driver.

- For output streams: commits the block for transmission, indicating that the data is ready to be streamed out.

This function must be called after processing or preparing each data block to maintain proper buffer flow and avoid data loss or stalling.

This function must be called after processing or preparing the data block returned by \ref vStreamGetBlock to maintain proper buffer flow and avoid data loss or stalling.

<b>Code Example</b>:

\code

  or when a block of outgoing data was streamed out.</td>

</tr>

<tr>

  <td> \ref VSTREAM_EVENT_OVERFLOW </td><td>  1  </td><td> Occurs when a block of data was overwritten because

  it was not released in time with \ref vStreamReleaseBlock function.</td>

  <td> \ref VSTREAM_EVENT_OVERFLOW </td><td>  1  </td><td> Occurs when a block of incoming data begins to be overwritten

  because it was not released in time using the \ref vStreamReleaseBlock function.</td>

</tr>

<tr>

  <td> \ref VSTREAM_EVENT_UNDERFLOW</td><td>  2  </td><td> Occurs when a block of outgoing data was not ready