MIPS/GAS: Correct the AFL_ASE_MASK macro
    
    Fix an issue with commit 8095d2f70e1a ("MIPS/GAS: Split Loongson MMI
    Instructions from loongson2f/3a"), AFL_ASE_MASK should be 0x0006ffff
    instead of 0x0004ffff.
    
    2018-07-27  Chenghua Xu  <paul.hua.gm@gmail.com>
                Maciej W. Rozycki  <macro@linux-mips.org>
    
    include/
    	* elf/mips.h (AFL_ASE_MASK): Correct typo.