libpixelflinger: Add ARM NEON optimized scanline_t32cb16

Reference benchmark results on Beagleboard (TI OMAP353x) at 500 MHz:
    scanline_t32cb16_c memory bandwidth: 31.63 MB/s
    scanline_t32cb16_neon memory bandwidth: 147.69 MB/s

It can dramatically improve the performance of boot animation.

Change-Id: I44916e550303a7ca84f5ed3226ba559dd7f0247f
2 files changed