kconfig: remove unneeded code for user-supplied values being out of range

This is a leftover from commit ce1fc934

 ("kconfig: do not clear
SYMBOL_DEF_USER when the value is out of range").

This code is now redundant because if a user-supplied value is out
of range, the value adjusted by sym_validate_range() differs, and
conf_unsaved has already been incremented a few lines above.

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