warp7: Allocate specific region of memory to OPTEE

Subtracts CONFIG_OPTEE_TZDRAM_SIZE from the available DRAM size.

On WaRP7 we simply define the OPTEE region as from the maximum DRAM address
minus CONFIG_OPTEE_TZDRAM_SIZE bytes.

Note the OPTEE boot process will itself subtract the DRAM region it lives
in from the memory map passed to Linux.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Tested-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>

board/warp7/warp7.c

@@ -58,6 +58,11 @@ int dram_init(void)
 {
 	gd->ram_size = PHYS_SDRAM_SIZE;
 
+	/* Subtract the defined OPTEE runtime firmware length */
+#ifdef CONFIG_OPTEE_TZDRAM_SIZE
+		gd->ram_size -= CONFIG_OPTEE_TZDRAM_SIZE;
+#endif
+
 	return 0;
 }