Some target are using llseek instead of _llseek like riscv,
nios2, hexagon, and openrisc.

Signed-off-by: Kito Cheng <kito.cheng@sifive.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210512101358.122781-1-kito.cheng@sifive.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>