drivers: irqchip: qcom-pdc: Move to an SoC independent compatible

Remove the sdm845 SoC specific compatible to make the driver
easily reusable across other SoC's with the same IP block.
This will reduce further churn adding any SoC specific
compatibles unless really needed.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Lina Iyer <ilina@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20191108092824.9773-7-rnayak@codeaurora.org