Inline xform_quant() in encode_block_intra().

Also inline some of the block calculations to assist the compiler to
not do silly things like calculating the same offset (or converting
between raster/transform block offset or block, mi and pixel unit)
many, many, many times.

Cycle times:
4x4:     584 ->   505 cycles (16% faster)
8x8:    1651 ->  1560 cycles (6% faster)
16x16:  7897 ->  7704 cycles (2.5% faster)
32x32: 16096 -> 15852 cycles (1.5% faster)

Overall, this saves about 0.5 seconds (1min49.8 -> 1min49.3) on the
first 50 frames of bus (speed 0) @ 1500kbps, i.e. 0.5% overall.

Change-Id: If3dd62453f8e2ab9d4ee616bc4ea956fb8874b80