Account for 1-D/2-D transform kernels for the eob modeling. To
maintain a smaller context cardinality, set the two 1-D transform
kernels in the same category. The difference in directions should
be largely covered by the scan order.

This and the previous CLs on nz_map context modeling together
improve the compression performance of level-map coefficient coding
system by 0.4% for lowres.

Change-Id: I8c4f03ca01ce3d248950d04bd1266f445b4227a0