commit 98f5f932254b88ce828bc8e4d1642d14e5854caa upstream.

The leak was found when opening/closing a serial port a great number of
time, increasing kmalloc-32 in slabinfo.

Each time the port was opened, dma_request_slave_channel() was called.
Then, in at_dma_xlate(), atslave was allocated with devm_kzalloc() and
never freed. (Well, it was free at module unload, but that's not what we
want).
So, here, kzalloc is more suited for the job since it has to be freed in
atc_free_chan_resources().

Cc: stable@vger.kernel.org
Fixes: bbe89c8e ("at_hdmac: move to generic DMA binding")
Reported-by: NMario Forner <m.forner@be4energy.com>
Suggested-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: NLudovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: NRichard Genoud <richard.genoud@gmail.com>
Signed-off-by: NVinod Koul <vkoul@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>