imx: add rom api support

i.MX8MN support loading images with rom api, so we implement
reuse board_return_to_bootrom to let ROM loading images.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index 3f93fe5..751c0b5 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -109,3 +109,7 @@
 	  NXP does NOT recommend to perform this calibration at each boot. One
 	  shall perform it on a new PCB and then use those values to program
 	  the ddrmc_cr_setting on relevant board file.
+
+config SPL_IMX_ROMAPI_LOADADDR
+	hex "Default load address to load image through ROM API"
+	depends on IMX8MN