Fixed coverity issue in acl_kernel.cpp: Type: Uninitialized scalar variable (UNINIT)

Function `l_copy_and_adjust_arguments_for_device` at `line 2164` uses `memory_migration.num_mem_objects`, but `memory_migration` has only been declared up until this point. I assume that since there has been no changes to `memory_migration`, upon declaration, the `num_mem_objects` should be set to 0. This assumption is reinforced by the second occurrence of `l_copy_and_adjust_arguments_for_device` at `line 2228` where `memory_migration.num_mem_objects = 0` is been initialized a few lines before.

Author: haoxian2

src/acl_kernel.cpp

@@ -1661,6 +1661,7 @@ static cl_int l_enqueue_kernel_with_type(
   acl_dev_kernel_invocation_image_t *invocation = 0;
   cl_context context;
   acl_mem_migrate_t memory_migration;
+  memory_migration.num_mem_objects = 0;
   cl_int status = CL_SUCCESS;
   int serialization_needed = 0;
   acl_assert_locked();