Remove redundant 'function's around lambda in vhdl-mode.el

Remove redundant 'function's around lambda in vhdl-mode.el

* lisp/progmodes/vhdl-mode.el (fboundp, vhdl-sort-alist, lambda)
(vhdl-create-mode-menu, vhdl-set-offset, vhdl-set-style)
(vhdl-regress-line, vhdl-align-inline-comment-region-1)
(vhdl-resolve-paths, vhdl-generate-makefile-1)
(vhdl-submit-bug-report): Remove redundant 'function's around lambda.