doc: [3/3] uniform the texinfo syntax for commands definition

doc: [3/3] uniform the texinfo syntax for commands definition

To avoid errors in the documentation, like the one fixed by change
http://openocd.zylin.com/6134/ , use a uniform notation across the
file so simple copy-paste will work.

Enclose every command within curly-brackets '{...}', even single
word commands.
Patch generated through:
	sed -i 's/^\(@deffn {[^{]*} \)\([^{][^ ]*\)/\1{\2}/' doc/openocd.texi
	sed -i 's/^\(@deffnx {[^{]*} \)\([^{][^ ]*\)/\1{\2}/' doc/openocd.texi

Change-Id: I41a8447d487ec8f6f32c2babcbc73ac21c769344
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6152
Tested-by: jenkins