kconfig: remove unused sym_get_env_prop() function

This function is unused since commit 104daea149c4 ("kconfig: reference
environment variables directly and remove 'option env='").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
2 files changed