Documentation/networking: netdev-FAQ typo corrections

Various typo fixes to netdev-FAQ.txt:
- capitalize Linux
- hyphenate dual-word adjectives
- minor punctuation fixes

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>