Use intrinsics for sse2 regular quantize

Remove dependency of this function on asm_offsets. ssse3/sse4 next.

Change quant_shift calculation so it be done using SIMD. Pre-calculate
as much as possible to simplify EOB selection.

Take advantage of qcoeff being zero'd by tying the if statements
together.

Speed parity with previous implementation with gcc x86_64 linux

Change-Id: Ife97556a1eca3a74b09def1a3d04084974dff1fb