kconfig: move sym_escape_string_value() to confdata.c

Now that sym_escape_string_value() is only used in confdata.c
it can be a 'static' function.

Rename it escape_string_value() because it is agnostic about
(struct sym *).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
3 files changed