imx: simplify dependency with SPL_BOOTROM_SUPPORT

For SoCs support ROM API, CONFIG_SPL_BOOTROM_SUPPORT is needed,
so use this macro to guard the code to avoid extend the list.

And drop the guard with structure definition, there is no need.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index 50f4c08..6b59752 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -170,7 +170,8 @@
 
 config SPL_IMX_ROMAPI_LOADADDR
 	hex "Default load address to load image through ROM API"
-	depends on IMX8_ROMAPI
+	depends on IMX8_ROMAPI || SPL_BOOTROM_SUPPORT
+	default 0
 
 config IMX_DCD_ADDR
 	hex "DCD Blocks location on the image"