enc_neon: convert FTransformWHT to intrinsics
enc_neon: convert FTransformWHT to intrinsics

slightly faster than the inline asm
in practice not much faster than the C-code in a full NEON build, but
still better overall in an Android-like one that only enables NEON for
certain files.

Change-Id: I69534016186064fd92476d5eabc0f53462d53146

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