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If the call to devm_spi_register_controller() fails on probe of the
Qualcomm Atheros AR934x/QCA95xx SPI driver, the spi_controller struct is
erroneously not freed.  Fix by switching over to the new
devm_spi_alloc_master() helper.

Moreover, the controller's clock is enabled on probe but not disabled if
any of the subsequent probe steps fail.

Finally, there's an ordering issue in ar934x_spi_remove() wherein the
clock is disabled even though the controller is not yet unregistered.
It is unregistered after ar934x_spi_remove() by the devres framework.
As long as it is not unregistered, SPI transfers may still be ongoing
and disabling the clock may break them.  It is not possible to use
devm_spi_register_controller() in this case, so move to the non-devm
variant.

All of these bugs have existed since the driver was first introduced,
so it seems fair to fix them together in a single commit.

Fixes: 047980c5

 ("spi: add driver for ar934x spi controller")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v5.7+: 5e844cc3: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v5.7+
Cc: Chuanhong Guo <gch981213@gmail.com>
Link: https://lore.kernel.org/r/1d58367d74d55741e0c2730a51a2b65012c8ab33.1607286887.git.lukas@wunner.de

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