spi: davinci: Unset POWERDOWN bit when releasing resources

spi: davinci: Unset POWERDOWN bit when releasing resources

On the OMAPL138, the SPI reference clock is provided by the Power and
Sleep Controller (PSC). The PSC's datasheet says that 'some peripherals
have special programming requirements and additional recommended steps
you must take before you can invoke the PSC module state transition'. I
didn't find more details in documentation but it appears that PSC needs
the SPI to clear the POWERDOWN bit before disabling the clock. Indeed,
when this bit is set, the PSC gets stuck in transitions from enable to
disable state.

Clear the POWERDOWN bit when releasing driver's resources

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Link: https://patch.msgid.link/20240624071745.17409-1-bastien.curutchet@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>