Adjust rtkaio patches to build with latest upstream
    
    Following commit upstream removed the definition for elfobjdir in
    favour of elf-objpfx.  Adjust rtkaio to build with this.
    
    commit 4134b50d6789c333707b1861a32314805bd0de5e
    Author: Joseph Myers <joseph@codesourcery.com>
    Date:   Wed May 21 16:52:08 2014 +0000
    
        Consistently use $(elf-objpfx).
    
        As previously noted
        <https://sourceware.org/ml/libc-alpha/2013-05/msg00696.html>,
        $(elf-objpfx) and $(elfobjdir) are redundant and should be
        consolidated.  This patch consolidates on $(elf-objpfx) (for
        consistency with $(csu-objpfx)), also changing direct uses of
        $(common-objpfx)elf/ to use $(elf-objpfx).