drm/amdgpu: add support for SMU debug option

SMU firmware expects the driver maintains error context
and doesn't interact with SMU any more when SMU errors
occurred. That will aid in debugging SMU firmware issues.

Add SMU debug option support for this request, it can be
enabled or disabled via amdgpu_smu_debug debugfs file.
Use a 32-bit mask to indicate corresponding debug modes.
Currently, only one mode(HALT_ON_ERROR) is supported.
When enabled, it brings hardware to a kind of halt state
so that no one can touch it any more in the envent of SMU
errors.

The dirver interacts with SMU via sending messages. And
threre are three ways to sending messages to SMU in current
implementation. Handle them respectively as following:

1, smu_cmn_send_smc_msg_with_param() for normal timeout cases

  Halt on any error.

2, smu_cmn_send_msg_without_waiting()/smu_cmn_wait_for_response()
for longer timeout cases

  Halt on errors apart from ETIME. Otherwise this way won't work.
  Let the user handle ETIME error in such a case.

3, smu_cmn_send_msg_without_waiting() for no waiting cases

  Halt on errors apart from ETIME. Otherwise second way won't work.

== Command Guide ==

1, enable HALT_ON_ERROR mode

 # echo 0x1 > /sys/kernel/debug/dri/0/amdgpu_smu_debug

2, disable HALT_ON_ERROR mode

 # echo 0x0 > /sys/kernel/debug/dri/0/amdgpu_smu_debug

v5:
 - Use bit mask to allow more debug features.(Evan)
 - Use WRAN() instead of BUG().(Evan)

v4:
 - Set to halt state instead of a simple hang.(Christian)

v3:
 - Use debugfs_create_bool().(Christian)
 - Put variable into smu_context struct.
 - Don't resend command when timeout.

v2:
 - Resend command when timeout.(Lijo)
 - Use debugfs file instead of module parameter.

Signed-off-by: Lang Yu <lang.yu@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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