kconfig: fix compatibility with older flex versions

Older flex versions require there be no space between options and
their arguments. For example '-P zconf' is not correct and should
be '-Pzconf'. This is for example the case for flex-2.5.4 shipped
with CentOS 5.8.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Message-Id: <9652ce148bddc1def484.1339241000@beantl019720>

     1.1 --- a/kconfig/Makefile	Mon Jul 02 19:49:02 2012 +0200
     1.2 +++ b/kconfig/Makefile	Sat Jul 14 19:52:58 2012 +0200
     1.3 @@ -88,7 +88,7 @@
     1.4  
     1.5  lex.zconf.c: zconf.l
     1.6  	@echo "  LEX    '$@'"
     1.7 -	@flex -L -P zconf -o $@ $<
     1.8 +	@flex -L -Pzconf -o$@ $<
     1.9  
    1.10  # Build C files
    1.11  %.o: %.c