Removing one blank line before printing documentation string

[Heime]

I have a documentation function called vajr-firp-doc that
calls the constant variable vajr-firp.  

Because of the newline before \\firp {PTL}, I get two blank lines
after printing (vajr-firp-doc).

How can I keep the value of vajr-firp intact, but
remove the additional blank line when doing 
"M-x vajr-firp-doc" ?


(defconst vajr-firp
  "
 \\firp {PTL}

 Portal to firp PTL.
"

(defun vajr-firp-doc ()

  ;; Print documentation about \vajr-firp.
  (:documentation
   (concat
     vajr-firp))
  )