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
11 files changed