drm/amd/display: Increase precision for bpp in DSC calculations

[Why?]
Many DSC variables and related functions use whole bits for bpp.

[How?]
Change variables and related functions to use 16ths of a bit for bpp.

Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Dillon Varone <[e-mail]>
Signed-off-by: Jun Lei <[e-mail]>
Reviewed-by: Wenjing Liu <[e-mail]>
Acked-by: Solomon Chiu <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dc_hw_types.h

···
 #endif
 
 	struct dc_crtc_timing_flags flags;
+	uint32_t dsc_fixed_bits_per_pixel_x16; /* DSC target bitrate in 1/16 of bpp (e.g. 128 -> 8bpp) */
 	struct dc_dsc_config dsc_cfg;
 };