drm/amdgpu: Fix the uninitialized variable warning

Check the user input and phy_id value range to fix
"Using uninitialized value phy_id"
Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -135,6 +135,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct file *f, const char __u
 		mutex_unlock(&psp->securedisplay_context.mutex);
 		break;
 	case 2:
+		if (size < 3 || phy_id >= TA_SECUREDISPLAY_MAX_PHY) {
+			dev_err(adev->dev, "Invalid input: %s\n", str);
+			return -EINVAL;
+		}
 		mutex_lock(&psp->securedisplay_context.mutex);
 		psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
 			TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);