scripts/spelling.txt: add "varible" pattern and fix typo instances

scripts/spelling.txt: add "varible" pattern and fix typo instances

Fix typos and add the following to the scripts/spelling.txt:

  varible||variable

While we are here, tidy up the comment blocks that fit in a single line
for drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c and
net/sctp/transport.c.

Link: http://lkml.kernel.org/r/1481573103-11329-11-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>