config: reorder the kernels sub-menu

Re-organise the sub-menu so that:
- the kernels list comes first,
- followed by kernels generic options
- followed by kernels specific options

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="unknown"

 reporter_url="http://iphonelinux.org/index.php/Glibc_toolchain_using_crosstool-NG"

 reporter_comment="An (experimental) toolchain targeting the Apple's iPhone."