VMCI: Remove handle_arr_calc_size()

VMCI: Remove handle_arr_calc_size()

Use struct_size() instead of handle_arr_calc_size().
This is much more conventional.

While at it, use size_add() when computing the needed size in
vmci_handle_arr_append_entry(). This prevents from (unlikely) overflow
when computing the new size to reallocate.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/84e7f2d8e7c4c2eab68f958307d56546978f76e3.1702125347.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>