drm/amd/display: set dcn315 lb bpp to 48

[Why & How]
Fix a typo for dcn315 line buffer bpp.
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn31/dcn31_fpu.c

@@ -222,7 +222,7 @@ struct _vcs_dpi_ip_params_st dcn3_15_ip = {
 	.maximum_dsc_bits_per_component = 10,
 	.dsc422_native_support = false,
 	.is_line_buffer_bpp_fixed = true,
-	.line_buffer_fixed_bpp = 49,
+	.line_buffer_fixed_bpp = 48,
 	.line_buffer_size_bits = 789504,
 	.max_line_buffer_lines = 12,
 	.writeback_interface_buffer_size_kbytes = 90,