scripts/spelling.txt: add more spellings to spelling.txt

Here are some of the more common spelling mistakes and typos that I've
found while fixing up spelling mistakes in the kernel since April 2020.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200714092837.173796-1-colin.king@canonical.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>