[lv_map] fix template size to 5
[lv_map] fix template size to 5

Cleanup context derivation for base levels by fixing the template size
to 5. No change to bitstream.

Change-Id: I496c74b386b8d8a4fb43c0b69add52a0a798a981

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom