drm/amd/display: Remove unused variable

Remove the variable clamshell_closed from the function
dcn10_align_pixel_clocks.

This was pointed by clang with the following warning:

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn10/dcn10_hw_sequencer.c:2063:7:
warning: variable 'clamshell_closed' set but not used
[-Wunused-but-set-variable]
    bool clamshell_closed = false;
         ^
Signed-off-by: Maíra Canal <maira.canal@usp.br>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -2060,14 +2060,11 @@ static int dcn10_align_pixel_clocks(struct dc *dc, int group_size,
 	uint32_t embedded_pix_clk_100hz;
 	uint16_t embedded_h_total;
 	uint16_t embedded_v_total;
-	bool clamshell_closed = false;
 	uint32_t dp_ref_clk_100hz =
 		dc->res_pool->dp_clock_source->ctx->dc->clk_mgr->dprefclk_khz*10;
 
 	if (dc->config.vblank_alignment_dto_params &&
 		dc->res_pool->dp_clock_source->funcs->override_dp_pix_clk) {
-		clamshell_closed =
-			(dc->config.vblank_alignment_dto_params >> 63);
 		embedded_h_total =
 			(dc->config.vblank_alignment_dto_params >> 32) & 0x7FFF;
 		embedded_v_total =