Tuning floating point RFFT for GCC 4.9.0
Tuning floating point RFFT for GCC 4.9.0

    Cortex-A53 (1.69GHz)
    GCC 4.9.0, with -O2
    Android-L, AArch64

    |   R2C FFT Time Cost in ms|
    |size|Ne10|pffft|pffft/Ne10|
    |  32| 118|  254|      215%|
    |  64| 126|  198|      157%|
    | 128| 109|  177|      162%|
    | 256| 126|  154|      122%|
    | 512| 122|  165|      135%|
    |1024| 143|  162|      113%|
    |2048| 153|  188|      123%|

    The larger the last column is, the faster Ne10 is.

Change-Id: I8921fc83afb8c7307ffd0fcb2a4bb1a88b349339

h6ah4i/Ne10,arnopaehler/Ne10,h6ah4i/Ne10,h6ah4i/Ne10,arnopaehler/Ne10,arnopaehler/Ne10,h6ah4i/Ne10,arnopaehler/Ne10,h6ah4i/Ne10,arnopaehler/Ne10