engines: separate declaration and assignment

engines: separate declaration and assignment

Separate the declaraction and assignment for some variables.

This is a prep patch for a Coccinelle script that converts
mallloc+memset(,0,) to calloc.

Part of this patch was created using the Coccinelle script below.

@@
identifier x;
expression y;
statement s;
type T;
@@

-T x = malloc(y);
+T x;
+x = malloc(y);
(
if (!x) s
|
if (x == NULL) s
|
)
memset(x, 0, y);

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>