refactor(plat/imx/imx): make imx io-storage logic for TBBR/FIP common

This commit makes imx image io-storage logic common for all
imx platform.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
Change-Id: I15045ac8f9dfa8cb714e32f9e7475d5eae4e86e4
diff --git a/plat/imx/imx8m/imx8mm/imx8mm_bl2_el3_setup.c b/plat/imx/imx8m/imx8mm/imx8mm_bl2_el3_setup.c
index 937774c..c39dd93 100644
--- a/plat/imx/imx8m/imx8mm/imx8mm_bl2_el3_setup.c
+++ b/plat/imx/imx8m/imx8mm/imx8mm_bl2_el3_setup.c
@@ -88,7 +88,7 @@
 	imx8mm_usdhc_setup();
 
 	/* Open handles to a FIP image */
-	plat_imx8mm_io_setup();
+	plat_imx_io_setup();
 }
 
 void bl2_el3_plat_arch_setup(void)