RISC-V: Fix build error

RISC-V: Fix build error

  - This build error was indroduced by "RISC-V: Implement movmemsi"
    and "RISC-V: Support -mpreferred-stack-boundary flag"

gcc/ChangeLog

2017-11-08  Kito Cheng  <kito.cheng@gmail.com>

        * config/riscv/riscv-protos.h (riscv_slow_unaligned_access_p):
        New extern.
        (MOVE_RATIO): Use riscv_slow_unaligned_access_p.
        config/riscv/riscv.c (predict.h): New include.
        (riscv_slow_unaligned_access_p): No longer static.
        (riscv_block_move_straight): Add require.
        config/riscv/riscv-protos.h (riscv_hard_regno_nregs): Delete.

From-SVN: r254554