drm/amdgpu/debugfs: fix error code when smc register accessors are NULL

Should be -EOPNOTSUPP.

Fixes: 5104fdf5 ("drm/amdgpu: Fix a null pointer access when the smc_rreg pointer is NULL")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

@@ -755,7 +755,7 @@ static ssize_t amdgpu_debugfs_regs_smc_read(struct file *f, char __user *buf,
 	int r;
 
 	if (!adev->smc_rreg)
-		return -EPERM;
+		return -EOPNOTSUPP;
 
 	if (size & 0x3 || *pos & 0x3)
 		return -EINVAL;
@@ -814,7 +814,7 @@ static ssize_t amdgpu_debugfs_regs_smc_write(struct file *f, const char __user *
 	int r;
 
 	if (!adev->smc_wreg)
-		return -EPERM;
+		return -EOPNOTSUPP;
 
 	if (size & 0x3 || *pos & 0x3)
 		return -EINVAL;