pitx-imx8m: enable support for dynamic memory variants

- add 'board_phys_sdram_size' function to calculate the total amount of
  memory appropriately.
- set PHYS_SDRAM_SIZE to the maximum possible value of 0xC0000000 (3 GiB)
- remove 'PHYS_SDRAM_2_SIZE' from board config file.
Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>

board/kontron/pitx-imx8m/pitx-imx8m.c

@@ -468,6 +468,18 @@ static int get_hw_rev(void)
 	         gpio_get_value(IMX_GPIO_NR(4, 0)) << 1 ) & 0x3 );
 }
 
+int board_phys_sdram_size(phys_size_t *memsize)
+{
+	/*
+	 * Get real memory size by testing available memory in a
+	 * given range starting at i.MX8M DRAM1 base address 0x40000000.
+	 */
+	*memsize = get_ram_size((long *)0x40000000, 0x100000000ULL);
+	debug("Memsize: %d MiB\n", (int)(*memsize >> 20));
+
+	return 0;
+}
+
 int board_init(void)
 {
 	/* 

include/configs/pitx-imx8m.h

@@ -216,14 +216,9 @@
 #define CONFIG_SYS_MALLOC_LEN		((CONFIG_ENV_SIZE + (2*1024) + (16*1024)) * 1024)
 
 #define PHYS_SDRAM			0x40000000
-#if 1
 #define PHYS_SDRAM_SIZE			0xC0000000 /* 3GB DDR in DRAM1 region */
 
 #define PHYS_SDRAM_2			0x100000000UL
-#define PHYS_SDRAM_2_SIZE		0x40000000 /* 1GB DDR in DRAM2 region */
-#else
-#define PHYS_SDRAM_SIZE			0x80000000 /* 2GB DDR in DRAM1 region */
-#endif
 
 #define CONFIG_SYS_MEMTEST_START	PHYS_SDRAM
 #define CONFIG_SYS_MEMTEST_END		(CONFIG_SYS_MEMTEST_START + \