drm/amd/pm: Fix an error handling path in vega10_enable_se_edc_force_stall_config()

In case of error after a amdgpu_gfx_rlc_enter_safe_mode() call, it is not
balanced by a corresponding amdgpu_gfx_rlc_exit_safe_mode() call.

Add the missing call.

Fixes: 9b7b8154 ("drm/amd/powerplay: added didt support for vega10")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>