spi: spacemit: introduce SpacemiT K1 SPI controller driver

spi: spacemit: introduce SpacemiT K1 SPI controller driver

This patch introduces the driver for the SPI controller found in the
SpacemiT K1 SoC.  Currently the driver supports master mode only.
The SPI hardware implements RX and TX FIFOs, 32 entries each, and
supports both PIO and DMA mode transfers.

Signed-off-by: Alex Elder <elder@riscstar.com>
Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://patch.msgid.link/20260502-spi-spacemit-k1-v10-2-f412e1ae8a34@riscstar.com
Signed-off-by: Mark Brown <broonie@kernel.org>