drm/amd/display: Remove always-false branches

[WHAT & HOW]
MacroTileSizeBytes is set to either 256 or 65535 and it is never
4096. Its branch is not taken, and should be removed. Similarly,
mode_422 is always 0 and thus ppe will always be 1. The ternary
operator should be removed.

This fixes 2 DEADCODE issues reported by Coverity.

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

drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c

···
 		*PixelPTEReqWidth = 32768.0 / BytePerPixel;
 		*PTERequestSize = 64;
 		FractionOfPTEReturnDrop = 0;
-	} else if (MacroTileSizeBytes == 4096) {
-		PixelPTEReqHeightPTEs = 1;
-		*PixelPTEReqHeight = MacroTileHeight;
-		*PixelPTEReqWidth = 8 * *MacroTileWidth;
-		*PTERequestSize = 64;
-		if (ScanDirection != dm_vert)
-			FractionOfPTEReturnDrop = 0;
-		else
-			FractionOfPTEReturnDrop = 7.0 / 8;
 	} else if (GPUVMMinPageSize == 4 && MacroTileSizeBytes > 4096) {
 		PixelPTEReqHeightPTEs = 16;
 		*PixelPTEReqHeight = 16 * BlockHeight256Bytes;

drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.c

···
 		const struct _vcs_dpi_display_pipe_source_params_st *pipe_src_param,
 		bool is_chroma)
 {
-	bool mode_422 = 0;
 	unsigned int vp_width = 0;
 	unsigned int vp_height = 0;
 	unsigned int data_pitch = 0;
 	unsigned int meta_pitch = 0;
-	unsigned int ppe = mode_422 ? 2 : 1;
+	unsigned int ppe = 1;
 	bool surf_linear;
 	bool surf_vert;
 	unsigned int bytes_per_element;