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-v2017.01.rst b/doc/develop/statistics/u-boot-stats-v2017.01.rst
index 4a996ea..6f14d7e 100644
--- a/doc/develop/statistics/u-boot-stats-v2017.01.rst
+++ b/doc/develop/statistics/u-boot-stats-v2017.01.rst
@@ -3,7 +3,7 @@
 Release Statistics for U-Boot v2017.01
 ======================================
 
-* Processed 883 csets from 137 developers
+* Processed 883 changesets from 137 developers
 
 * 29 employers found