drm/amd/display: Initialize denominator defaults to 1

[WHAT & HOW]
Variables, used as denominators and maybe not assigned to other values,
should be initialized to non-zero to avoid DIVIDE_BY_ZERO, as reported
by Coverity.

Reviewed-by: Austin Zheng <[e-mail]>
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]>
(cherry picked from commit e2c4c6c10542ccfe4a0830bb6c9fd5b177b7bbb7)

drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c

···
 {
 	*BytePerPixelDETY = 0;
 	*BytePerPixelDETC = 0;
-	*BytePerPixelY = 0;
-	*BytePerPixelC = 0;
+	*BytePerPixelY = 1;
+	*BytePerPixelC = 1;
 
 	if (SourcePixelFormat == dml2_444_64) {
 		*BytePerPixelDETY = 8;