kconfig/zconf.l: do not ask to generate backup

This avoids the creation of a top-level `lex.backup' when the lexer gets
re-generated.
Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>

scripts/kconfig/zconf.l

-%option backup nostdinit noyywrap never-interactive full ecs
-%option 8bit backup nodefault perf-report perf-report
+%option nostdinit noyywrap never-interactive full ecs
+%option 8bit nodefault perf-report perf-report
 %option noinput
 %x COMMAND HELP STRING PARAM
 %{