Fix test memory allocation

Fix error in memory allocation in test code, which was triggering an
error in test_memory_buffer_allocator.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_pkcs7.function b/tests/suites/test_suite_pkcs7.function
index 14a0882..e396140 100644
--- a/tests/suites/test_suite_pkcs7.function
+++ b/tests/suites/test_suite_pkcs7.function
@@ -75,7 +75,7 @@
     TEST_ASSERT( file != NULL );
 
     datalen = st.st_size;
-    data = mbedtls_calloc( datalen, 1 );
+    ASSERT_ALLOC( data, datalen );
     TEST_ASSERT( data != NULL );
 
     buflen = fread( (void *)data , sizeof( unsigned char ), datalen, file );
@@ -154,7 +154,7 @@
     TEST_ASSERT( file != NULL );
 
     datalen = st.st_size;
-    data = ( unsigned char* ) calloc( datalen, sizeof(unsigned char) );
+    ASSERT_ALLOC( data, datalen );
     buflen = fread( ( void * )data , sizeof( unsigned char ), datalen, file );
     TEST_ASSERT( buflen == datalen );