tty: serial: qcom_geni_serial: Wakeup IRQ cleanup

This patch is the continuation of below mentioned commits which adds wakeup
feature over the UART RX line.
1)commit 3e4aaea7 ("tty: serial: qcom_geni_serial: IRQ cleanup")[v2]
2)commit 8b7103f3

 ("tty: serial: qcom_geni_serial: Wakeup over UART
  RX")[v2]

The following cleanup is done based on upstream comment received on
subsequent versions of the above-mentioned commits to simplifying the code.
 - Use devm_kasprintf API in place of scnprintf.
 - Use dev_pm_set_dedicated_wake_irq API that will take care of
   requesting and attaching wakeup irqs for devices. Also, it sets wakeirq
   status to WAKE_IRQ_DEDICATED_ALLOCATED as a result enabling/disabling of
   wake irq will be managed by suspend/resume framework. We can remove the
   code for enabling and disabling of wake irq from the this driver.
 - Use platform_get_irq_optional API to get optional wakeup IRQ for
   device.
 - Move ISR registration later in probe after uart port gets register with
   serial core.

Patch link:
 - https://patchwork.kernel.org/patch/11189717/ (v3)
 - https://patchwork.kernel.org/patch/11227435/ (v4)
 - https://patchwork.kernel.org/patch/11241669/ (v5)
 - https://patchwork.kernel.org/patch/11258045/ (v6)

Signed-off-by: Akash Asthana <akashast@codeaurora.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1578321905-25843-2-git-send-email-akashast@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>