remoteproc: qcom: q6v5: Avoid disabling handover IRQ twice

enable_irq() and disable_irq() are reference counted, so we must make sure
that each enable_irq() is always paired with a single disable_irq(). If we
call disable_irq() twice followed by just a single enable_irq(), the IRQ
will remain disabled forever.

For the error handling path in qcom_q6v5_wait_for_start(), disable_irq()
will end up being called twice, because disable_irq() also happens in
qcom_q6v5_unprepare() when rolling back the call to qcom_q6v5_prepare().

Fix this by dropping disable_irq() in qcom_q6v5_wait_for_start(). Since
qcom_q6v5_prepare() is the function that calls enable_irq(), it makes more
sense to have the rollback handled always by qcom_q6v5_unprepare().

Fixes: 3b415c8fb263 ("remoteproc: q6v5: Extract common resource handling")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Link: https://lore.kernel.org/r/20250820-rproc-qcom-q6v5-fixes-v2-1-910b1a3aff71@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>