doc: complete setexpr configuration information

Add missing information to the configuration section of the setexpr
man-page.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/setexpr.rst b/doc/usage/cmd/setexpr.rst
index 2e511b1..4d19fa3 100644
--- a/doc/usage/cmd/setexpr.rst
+++ b/doc/usage/cmd/setexpr.rst
@@ -138,7 +138,10 @@
 Configuration
 -------------
 
-The setexpr gsub and sub operations are only available if CONFIG_REGEX=y.
+* The *setexpr* command is only available if CMD_SETEXPR=y.
+* The *setexpr fmt* sub-command is only available if CMD_SETEXPR_FMT=y.
+* The *setexpr gsub* and *setexpr sub* sub-commands are only available if
+  CONFIG_REGEX=y.
 
 Return value
 ------------