refactor(imx): update config of mbedtls support

Pull in MbedTLS support for sha512 when greater than sha256 is required
based on refactoring for hash algorithm selection for Measured Boot.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I489392133435436a16edced1d810bc5204ba608f
diff --git a/plat/imx/imx8m/imx8mm/platform.mk b/plat/imx/imx8m/imx8mm/platform.mk
index 0cce7ca..60fa325 100644
--- a/plat/imx/imx8m/imx8mm/platform.mk
+++ b/plat/imx/imx8m/imx8mm/platform.mk
@@ -162,6 +162,10 @@
     $(info Including ${MEASURED_BOOT_MK})
     include ${MEASURED_BOOT_MK}
 
+ifneq (${MBOOT_EL_HASH_ALG}, sha256)
+    $(eval $(call add_define,TF_MBEDTLS_MBOOT_USE_SHA512))
+endif
+
 BL2_SOURCES		+=	plat/imx/imx8m/imx8m_measured_boot.c	\
 				plat/imx/imx8m/imx8m_dyn_cfg_helpers.c	\
 				${EVENT_LOG_SOURCES}