x86: Remove the secondary encoding for ctest.

There are two encodings for each opcode F6/F7 in ctest, but the second one
is never used, so remove it to reduce the size of opcode_tbl.h.

opcodes/ChangeLog:

        * i386-opc.tbl: Removed the secondary insn template for ctest.
        * i386-tbl.h: Regenerated.