doc: Use "changesets" not "csets" in statistics pages

To make things more human readable, say "changesets from" rather than
"csets from" in all our historical pages here. Moving forward this has
been changed in our gitdm with b034e399e31a ("gitdm: fix typo csets").

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/develop/statistics/u-boot-stats-v2018.11.rst b/doc/develop/statistics/u-boot-stats-v2018.11.rst
index 8c84bb8..6ce39b9 100644
--- a/doc/develop/statistics/u-boot-stats-v2018.11.rst
+++ b/doc/develop/statistics/u-boot-stats-v2018.11.rst
@@ -3,7 +3,7 @@
 Release Statistics for U-Boot v2018.11
 ======================================
 
-* Processed 1105 csets from 130 developers
+* Processed 1105 changesets from 130 developers
 
 * 31 employers found