read_tile_info: simplify EXT_TILE ifdefs
read_tile_info: simplify EXT_TILE ifdefs

remove else and return immediately from the large_scale_tile branch

Change-Id: I934fa46c6abd7d65aeb4ef177163744a145ca046

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