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-v2012.10.rst b/doc/develop/statistics/u-boot-stats-v2012.10.rst
index ec06b57..715ec34 100644
--- a/doc/develop/statistics/u-boot-stats-v2012.10.rst
+++ b/doc/develop/statistics/u-boot-stats-v2012.10.rst
@@ -3,7 +3,7 @@
 Release Statistics for U-Boot v2012.12
 ======================================
 
-* Processed 925 csets from 134 developers
+* Processed 925 changesets from 134 developers
 
 * 31 employers found