If the irq is enabled after the spi si registered, there can be a race
with the initialization of the devices on the spi bus.

Eg:
mtk-spi 1100a000.spi: spi-mem transfer timeout
spi-nor: probe of spi0.0 failed with error -110
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000010
...
Call trace:
 mtk_spi_can_dma+0x0/0x2c

Fixes: c6f78746 ("spi: mediatek: Enable irq when pdata is ready")
Reported-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/20221225-mtk-spi-fixes-v1-0-bb6c14c232f8@chromium.orgSigned-off-by: Mark Brown <broonie@kernel.org>