ST, stm32 flexible memory controller Drive
Required properties:
- compatible	: "st,stm32-fmc"
- reg		: fmc controller base address
- clocks	: fmc controller clock
u-boot,dm-pre-reloc: flag to initialize memory before relocation.

on-board sdram memory attributes:
- st,sdram-control : parameters for sdram configuration, in this order:
  number of columns
  number of rows
  memory width
  number of intenal banks in memory
  cas latency
  read burst enable or disable
  read pipe delay

- st,sdram-timing: timings for sdram, in this order:
  tmrd
  txsr
  tras
  trc
  trp
  trcd

There is device tree include file at :
include/dt-bindings/memory/stm32-sdram.h to define sdram control and timing
parameters as MACROS.

Example:
	fmc: fmc@A0000000 {
	     compatible = "st,stm32-fmc";
	     reg = <0xA0000000 0x1000>;
	     clocks = <&rcc 0 64>;
	     u-boot,dm-pre-reloc;
	};

	&fmc {
		pinctrl-0 = <&fmc_pins>;
		pinctrl-names = "default";
		status = "okay";

		/* sdram memory configuration from sdram datasheet */
		bank1: bank@0 {
		       st,sdram-control = /bits/ 8 <NO_COL_8 NO_ROW_12 MWIDTH_16 BANKS_2
						CAS_3 RD_BURST_EN RD_PIPE_DL_0>;
		       st,sdram-timing = /bits/ 8 <TMRD_1 TXSR_60 TRAS_42 TRC_60 TRP_18
						TRCD_18>;
		};

		/* sdram memory configuration from sdram datasheet */
		bank2: bank@1 {
		       st,sdram-control = /bits/ 8 <NO_COL_8 NO_ROW_12 MWIDTH_16 BANKS_2
						CAS_3 RD_BURST_EN RD_PIPE_DL_0>;
		       st,sdram-timing = /bits/ 8 <TMRD_1 TXSR_60 TRAS_42 TRC_60 TRP_18
						TRCD_18>;
		};
	}
