Original stdio read use readv as default syscall,calling vfs_read twice will
reduce I/O throughout, use syscall read instead with buffer if possible

Issue:I70LQ0
Test: libc-test, benchmark
Signed-off-by: Nrobottoy <wangyaofeng.wang@huawei.com>
Change-Id: I2e5c0298fcd665edb3228ca400ee77fbf25a298c