wcn36xx: Fix DMA channel enable/disable cycle

Right now we have a broken sequence where we enable DMA channel interrupts
which can be left enabled and never disabled if we hit an error path.

Worse still when we unload the driver, the DMA channel interrupt bits are
left intact. About the only saving grace here is that we do remember to
disable the wcnss interrupt when unload the driver.

Fixes: 8e84c258 ("wcn36xx: mac80211 driver for Qualcomm WCN3660/WCN3680 hardware")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211105122152.1580542-2-bryan.odonoghue@linaro.org