api-parse-options.txt: fix description of OPT_CMDMODE

The description of the 'OPT_CMDMODE' macro states that "enum_val is
set to int_var when ...", but it's the other way around, 'int_var' is
set to 'enum_val'.  Fix this.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-parse-options.txt

@@ -236,7 +236,7 @@ There are some macros to easily define options:
 `OPT_CMDMODE(short, long, &int_var, description, enum_val)`::
 	Define an "operation mode" option, only one of which in the same
 	group of "operating mode" options that share the same `int_var`
-	can be given by the user. `enum_val` is set to `int_var` when the
+	can be given by the user. `int_var` is set to `enum_val` when the
 	option is used, but an error is reported if other "operating mode"
 	option has already set its value to the same `int_var`.