The GDMA layer used `max_data_burst_size == 0` as the only way to disable the
data burst. That conflicts with the upstream drivers' convention where a zeroed
config struct means "unset", so users had no way to ask for the driver default
burst size.
GDMA now treats both 0 and 1 as "no data burst": a single-beat burst has no
benefit over the non-burst mode. The MSPI alignment constraint under Flash
Encryption / PSRAM ECC still takes precedence and is reported with a warning.
The upstream drivers using GDMA now apply their own default burst size (16
bytes) when the user leaves `dma_burst_size` as 0, following the UHCI driver:
- esp_async_crc (AHB / AXI GDMA backend)
- esp_async_memcpy (AHB / AXI / LP-AHB / DW_GDMA backend)
Callers that really want no burst can now set `dma_burst_size` to 1.
Add a blocking wrapper for async memcpy so simple users can wait for one DMA copy without writing their own ISR callback and semaphore plumbing. Update functional tests and documentation to use the simpler API where async completion handling is not needed.
Co-authored-by: Cursor <cursoragent@cursor.com>
