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>

reporter_name="Giammarco Zacheo"

reporter_url=""

reporter_comment=""