Revert "printk: make reading the kernel log flush pending lines"

Revert "printk: make reading the kernel log flush pending lines"

This reverts commit 6b5d3f0745f186baf7179e69eeb3e46e5939d766.

It turns out that this flushes things much too aggressiverly, and causes
lines to break up when the system logger races with new continuation
lines being printed.

There's a pending patch to make printk() flushing much more
straightforward, but it's too invasive for 4.9, so in the meantime let's
just not make the system message logging flush continuation lines.
They'll be flushed by the final newline anyway.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>