chore(qemu): remove duplicate define

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Change-Id: Id18abe80ab56fd51a9c2c1206b22d87f1e3871eb
diff --git a/plat/qemu/qemu/platform.mk b/plat/qemu/qemu/platform.mk
index 066554a..cf1b3a8 100644
--- a/plat/qemu/qemu/platform.mk
+++ b/plat/qemu/qemu/platform.mk
@@ -96,10 +96,6 @@
     $(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/qemu/qemu/qemu_measured_boot.c	\
 				plat/qemu/qemu/qemu_helpers.c		\
 				${EVENT_LOG_SOURCES}