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-v2011.12.rst b/doc/develop/statistics/u-boot-stats-v2011.12.rst
index cb9244f..3d2fdcd 100644
--- a/doc/develop/statistics/u-boot-stats-v2011.12.rst
+++ b/doc/develop/statistics/u-boot-stats-v2011.12.rst
@@ -3,7 +3,7 @@
 Release Statistics for U-Boot v2011.12
 ======================================
 
-* Processed 1530 csets from 146 developers
+* Processed 1530 changesets from 146 developers
 
 * 34 employers found