board: samsung: reserve memory for the secure firmware

Since more than one board requires memory reservation
for the secure firmware, the reservation code can be
made in a common code.
Now, to reserve some part of the the last bank,
board config should define:
- CONFIG_TZSW_RESERVED_DRAM - len in bytes
- CONFIG_NR_DRAM_BANKS - number of memory banks

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Akshay Saraswat <akshay.s@samsung.com>
Cc: Hyungwon Hwang <human.hwang@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

board/samsung/common/board.c

@@ -82,7 +82,13 @@ int board_init(void)
 	}
 	boot_temp_check();
 #endif
+#ifdef CONFIG_TZSW_RESERVED_DRAM_SIZE
+	/* The last few MB of memory can be reserved for secure firmware */
+	ulong size = CONFIG_TZSW_RESERVED_DRAM_SIZE;
 
+	gd->ram_size -= size;
+	gd->bd->bi_dram[CONFIG_NR_DRAM_BANKS - 1].size -= size;
+#endif
 	return exynos_init();
 }