board: phycore_imx8mm: update RAM timings

Updated RAM timings with new generated settings using
DDR Tool v3.6.0_22-aa018543.
Provide functions for 1GB, 4GB and revision 7 variants.

Signed-off-by: INgo Rah <ingo.rah@linutronix.de>
Reviewed-by: Gregor Herburger <gregor.herburger@linutronix.de>
Reviewed-by: Benedikt Spranger <b.spranger@linutronix.de>
Tested-by: Yannic Moog <y.moog@phytec.de>

board/phytec/phycore_imx8mm/lpddr4_timing.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2025 PHYTEC Messtechnik GmbH
+ */
+
+#ifndef __LPDDR4_TIMING_H__
+#define __LPDDR4_TIMING_H__
+
+void set_dram_timings_1gb(void);
+void set_dram_timings_4gb(void);
+void set_dram_timings_rev7(void);
+
+#endif /* __LPDDR4_TIMING_H__ */