riscv: remove redundant logical constraint.

After

    if (ret) return ret;

we know that ret is zero. Don't check it again.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>