x86/doc: Fix Documentation/x86/earlyprintk.txt

Fix a few issues in Documentation/x86/earlyprintk.txt:

- correct typos, punctuation, missing word, wrong word
- change product name from Netchip to NetChip
- expand where to add "earlyprintk=dbg"

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Link: http://lkml.kernel.org/r/d0c40ac3-7659-6374-dbda-23d3d2577f30@infradead.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>