spi: davinci: Adapt transfer's timeout to transfer's length

The timeout used when waiting for transfer's completion is always set to
HZ. This isn't enough if a transfer is too large or if the bus speed is
too low.

Use the bus speed and the transfer length to calculate an appropriate
timeout

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Link: https://patch.msgid.link/20240828063131.10507-1-bastien.curutchet@bootlin.com


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