fix(io_stm32image): invalidate cache on local buf

When retrieving data from stm32 image file, the header is removed with
a memcpy that shifts the data to overwrite the useless header for next
binary.

STM32 binary from boot device:
|-------------------------------------|
| header | payload                    |
|-------------------------------------|

After the memcpy:
|-------------------------------------|
| payload                    | remain |
|-------------------------------------|

But the remaining data after the shifted payload is still in
the cache. As it is of no use for anyone, just invalidate the cache
at this address.
This is required if the DDR is mapped secure in BL2, and the secure
access is forbidden in BL33, or else TZC-400 issues an error.

Change-Id: Ice2af3b1ca49eccb79bfc62db60437e259d344ca
Signed-off-by: Yann Gautier <yann.gautier@st.com>

drivers/st/io/io_stm32image.c

@@ -346,6 +346,9 @@ static int stm32image_partition_read(io_entity_t *entity, uintptr_t buffer,
 			return result;
 		}
 
+		inv_dcache_range(round_up((uintptr_t)(local_buffer + length - hdr_sz),
+					  CACHE_WRITEBACK_GRANULE), *length_read - length + hdr_sz);
+
 		io_close(backend_handle);
 	}