The encoding of PREF, CACHE, LLD and SCD instruction changed in MIPS32R6.
Additionally, the hint codes in PREF instruction greater than or
equal to 24 generate Reserved Instruction Exception.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>