libublk: add UblkQueue::complete_io_cmd_with_auto_buf_reg() and ::sub…

[ming1]

…mit_fetch_commands_with_auto_buf_reg()

Added Methods

1. UblkQueue::complete_io_cmd_with_auto_buf_reg()

This method provides zero-copy IO completion for non-async/await cases when UBLK_F_AUTO_BUF_REG is enabled. Key features:

• Takes tag, buf_reg_data: &sys::ublk_auto_buf_reg, and res: Result<UblkIORes, UblkError>
• Supports all the same result types as the regular complete_io_cmd() method
• Handles fat completion features (batch and zoned append)
• Uses auto buffer registration data to avoid manual buffer management

2. UblkQueue::submit_fetch_commands_with_auto_buf_reg()

Location: src/io.rs:1023-1049

This method initializes the queue with auto buffer registration for zero-copy operations. Key features:

• Takes buf_reg_data_list: &[sys::ublk_auto_buf_reg] for each queue depth slot
• Validates that auto buffer registration is supported
• Ensures the provided list has enough entries for all queue slots
• Uses the internal __queue_io_cmd() method with auto buffer address encoding

Implementation Details

Both methods:

• Use the existing bindings::ublk_auto_buf_reg_to_sqe_addr() function to encode buffer registration data
• Leverage the existing __queue_io_cmd() infrastructure with the sqe_addr parameter
• Follow the same patterns as the async versions (submit_io_cmd_with_auto_buf_reg)
• Include proper documentation and safety assertions

Also add test case for covering the added APIs.