fix(qemu): fix EL3-SPMC data store alignment

With PLAT=qemu, the EL3-SPMC data store is provided as an array of
uint8_t and implicitly with a 1 byte alignment. But the way the data
store is used it must have a larger alignment, so change to double-word
alignment for maximum compatibility.

Change-Id: I4e9b901889078fee4b87f8333257bdc076386572
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/plat/qemu/common/qemu_common.c b/plat/qemu/common/qemu_common.c
index 0702673..9ccb2c8 100644
--- a/plat/qemu/common/qemu_common.c
+++ b/plat/qemu/common/qemu_common.c
@@ -178,7 +178,7 @@
  */
 #define PLAT_SPMC_SHMEM_DATASTORE_SIZE 64 * 1024
 
-uint8_t plat_spmc_shmem_datastore[PLAT_SPMC_SHMEM_DATASTORE_SIZE];
+uint8_t plat_spmc_shmem_datastore[PLAT_SPMC_SHMEM_DATASTORE_SIZE] __aligned(2 * sizeof(long));
 
 int plat_spmc_shmem_datastore_get(uint8_t **datastore, size_t *size)
 {