scripts/spelling.txt: spelling of uninitialized

I just did a spelling mistake of uninitialized and wrote that as
unintialized.  Fortunately I noticed it in my final review.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>