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-v2017.11.rst b/doc/develop/statistics/u-boot-stats-v2017.11.rst
index 700e09d..ba2f9e3 100644
--- a/doc/develop/statistics/u-boot-stats-v2017.11.rst
+++ b/doc/develop/statistics/u-boot-stats-v2017.11.rst
@@ -3,7 +3,7 @@
 Release Statistics for U-Boot v2017.11
 ======================================
 
-* Processed 989 csets from 123 developers
+* Processed 989 changesets from 123 developers
 
 * 28 employers found