drm/amd/pm: smu7: Remove stale error check in smu7_hwmgr_backend_init

smu7_hwmgr_backend_init() is responsible for initializing the SMU7 power
management backend. It allocates and sets up the backend structure,
initializes voltage tables, configures dependency tables, and prepares
platform-specific power and clock parameters.

The function follows a typical pattern where each initialization step
returns a status in "result", and failures are handled via a common
"goto fail" path that performs cleanup.

Commit 2c21648bb814 ("drm/amd/pm/smu7: Remove non-functional SMU7
voltage dependency on DAL") removed a function call in this
initialization sequence, but left behind the corresponding error check.

As a result, "result" is checked twice without being updated in between:

result = smu7_init_voltage_dependency_on_display_clock_table(hwmgr);
if (result)
goto fail;

...

if (result)
goto fail;

The second check is redundant and unreachable for any new failure, since
no operation modifies "result" between the two checks. This triggers a
Smatch warning about a duplicate zero check and reduces code clarity.

Remove the stale error check to keep the control flow correct and
readable.

Fixes: 9f49e3d4cb86 ("drm/amd/pm/smu7: Remove non-functional SMU7 voltage dependency on DAL")
Reported-by: Dan Carpenter <error27@gmail.com>
Cc: Timur Kristóf <timur.kristof@gmail.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>