drm/amd/display: Remove useless assignments and variables

[WHAT & HOW]
misc0, temp and split_pipe are assigned but immediately re-assigned
to other values. The early assignments are useless and are removed.
Unused variables are removed as well.

This fixes 5 UNUSED_VALUE issues reported by Coverity.

Reviewed-by: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Alex Hung <[e-mail]>
Signed-off-by: Tom Chung <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c

···
 		r2 = test_pipe->plane_res.scl_data.recout;
 		r2_r = r2.x + r2.width;
 		r2_b = r2.y + r2.height;
-		split_pipe = test_pipe;
 
 		/**
 		 * There is another half plane on same layer because of

drivers/gpu/drm/amd/display/dc/dce/dce_stream_encoder.c

···
 	uint32_t misc1 = 0;
 	uint32_t h_blank;
 	uint32_t h_back_porch;
-	uint8_t synchronous_clock = 0; /* asynchronous mode */
 	uint8_t colorimetry_bpc;
 	uint8_t dynamic_range_rgb = 0; /*full range*/
 	uint8_t dynamic_range_ycbcr = 1; /*bt709*/
···
 		break;
 	}
 
-	misc0 = misc0 | synchronous_clock;
 	misc0 = colorimetry_bpc << 5;
 
 	if (REG(DP_MSA_TIMING_PARAM1)) {

drivers/gpu/drm/amd/display/dc/dce110/dce110_mem_input_v.c

···
 		mmUNP_GRPH_PRIMARY_SURFACE_ADDRESS_HIGH_C,
 		value);
 
-	temp = 0;
 	value = 0;
 	temp = address.low_part >>
 	UNP_GRPH_PRIMARY_SURFACE_ADDRESS_C__GRPH_PRIMARY_SURFACE_ADDRESS_C__SHIFT;
···
 		mmUNP_GRPH_PRIMARY_SURFACE_ADDRESS_HIGH_L,
 		value);
 
-	temp = 0;
 	value = 0;
 	temp = address.low_part >>
 	UNP_GRPH_PRIMARY_SURFACE_ADDRESS_L__GRPH_PRIMARY_SURFACE_ADDRESS_L__SHIFT;

drivers/gpu/drm/amd/display/dc/dio/dcn10/dcn10_stream_encoder.c

···
 	uint32_t misc1 = 0;
 	uint32_t h_blank;
 	uint32_t h_back_porch;
-	uint8_t synchronous_clock = 0; /* asynchronous mode */
 	uint8_t colorimetry_bpc;
 	uint8_t dp_pixel_encoding = 0;
 	uint8_t dp_component_depth = 0;
···
 		break;
 	}
 
-	misc0 = misc0 | synchronous_clock;
 	misc0 = colorimetry_bpc << 5;
 
 	switch (output_color_space) {

drivers/gpu/drm/amd/display/dc/dio/dcn401/dcn401_dio_stream_encoder.c

···
 	uint32_t misc1 = 0;
 	uint32_t h_blank;
 	uint32_t h_back_porch;
-	uint8_t synchronous_clock = 0; /* asynchronous mode */
 	uint8_t colorimetry_bpc;
 	uint8_t dp_pixel_encoding = 0;
 	uint8_t dp_component_depth = 0;
···
 		break;
 	}
 
-	misc0 = misc0 | synchronous_clock;
 	misc0 = colorimetry_bpc << 5;
 
 	switch (output_color_space) {