kern-tools: tools/kconf_check: modify grep pattern

kern-tools: tools/kconf_check: modify grep pattern

Integrating the following kern tools patch:

    The cmd line, <grep '^[  ]*\(menu\)*config '>, can't
    match all expect config options.

    This is because that it is not always a single space after 'config'
    in kernel-source/*/.../Kconfig. e.g. "config IP_VS_IPV6" in
    net/netfilter/ipvs/Kconfig

    So we should change the cmd to grep '^[  ]*\(menu\)*config\s'.

    Signed-off-by: Hongzhi.Song <hongzhi.song@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>