firmware: qcom: scm: Register gunyah watchdog device

firmware: qcom: scm: Register gunyah watchdog device

To restrict Gunyah watchdog initialization to Qualcomm platforms running
under the Gunyah Hypervisor, register the watchdog device in the QCOM
SCM driver.

When Gunyah is not present or Gunyah emulates MMIO-based watchdog, we
expect Qualcomm watchdog or ARM SBSA watchdog device to be present in
the devicetree. First, we make sure we're running under the Gunyah
Hypervisor. Then we move to check if any of the above mentioned
watchdog device nodes are present, if not then we proceed to register
the SMC-based Gunyah watchdog device.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Tested-by: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Hrishabh Rajput <hrishabh.rajput@oss.qualcomm.com>
Signed-off-by: Pavankumar Kondeti <pavan.kondeti@oss.qualcomm.com>
Tested-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260311-gunyah_watchdog-v8-1-4c1c0689de22@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>