drm/amd/display: Prevent VStartup Overflow

[WHY & HOW]
Fixed Overflow issue by clamping VStartup to max value of register.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Ryan Seto <ryanseto@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>

drivers/gpu/drm/amd/display/dc/dml2/display_mode_core.c

@@ -32,6 +32,7 @@
 #define DML2_MAX_FMT_420_BUFFER_WIDTH 4096
 #define TB_BORROWED_MAX 400
+#define DML_MAX_VSTARTUP_START 1023
 // ---------------------------
 //  Declaration Begins
@@ -6210,6 +6211,7 @@ static dml_uint_t CalculateMaxVStartup(
 	dml_print("DML::%s: vblank_avail = %u\n", __func__, vblank_avail);
 	dml_print("DML::%s: max_vstartup_lines = %u\n", __func__, max_vstartup_lines);
 #endif
+	max_vstartup_lines = (dml_uint_t) dml_min(max_vstartup_lines, DML_MAX_VSTARTUP_START);
 	return max_vstartup_lines;
 }