spi: rockchip-sfc: Optimize the judgment mechanism completed by the controller

There is very little data left in fifo, and the controller will
complete the transmission in a short period of time, so
use readl_poll_timeout() for busy wait 10us to accelerate response.

Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Link: https://patch.msgid.link/20241203013513.2628810-1-jon.lin@rock-chips.com


Signed-off-by: Mark Brown <broonie@kernel.org>