efi_mem_sort: use list_for_each_entry_safe instead

efi_mem_sort: use list_for_each_entry_safe instead

Use list_for_each_entry_safe and comparisons against the current and
next efi_mem_desc. This reduces the computation required for merging
regions, prevents unnecessary additional iterations of the list, and
requires less temporary values.

Signed-off-by: Randolph Sapp <rs@ti.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>