Remove the unnecessary full_x86_64 and full_mips64.

For historical reason, the aosp_* products were named full_*.
We keep the full, full_x86 and full_mips in case some tools still
reference these legacy names; But no reason the have the full_* product
names for the new 64-bit archs.

Change-Id: I240ed0c6ded0ded2d80603bd0c5ff24750999afc