spi: add ch341a usb2spi driver

Add a driver for the QiHeng Electronics ch341a USB-to-SPI adapter.

This driver is loosely based on the ch341a module from the flashrom project.

Signed-off-by: Johannes Thumshirn <jth@kernel.org>
Link: https://patch.msgid.link/20240708-spi-ch341a-v3-1-cf7f9b2c1e31@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>