scripts/spelling.txt: add "overflw"

Add typo "overflw" for "overflow".  This typo was found and fixed in
drivers/clocksource/timer-pistachio.c.

Link: https://lore.kernel.org/lkml/20210305090315.384547-1-drew@beagleboard.org/
Link: https://lkml.kernel.org/r/20210305095151.388182-1-drew@beagleboard.org
Signed-off-by: Drew Fustini <drew@beagleboard.org>
Suggested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/scripts/spelling.txt b/scripts/spelling.txt
index 2e6a230..7b6a012 100644
--- a/scripts/spelling.txt
+++ b/scripts/spelling.txt
@@ -1028,6 +1028,7 @@
 overaall||overall
 overhread||overhead
 overlaping||overlapping
+overflw||overflow
 overlfow||overflow
 overide||override
 overrided||overridden