(e)glibc.inc: add minimal sane kernel versions, move from bitbake.conf

(e)glibc.inc: add minimal sane kernel versions, move from bitbake.conf

(e)glibc is configured for OLDEST_KERNEL, certain target architectures have
specific requirements for kernel versions, if that are not satisfied (e)glibc
reconfigures itself with what it think more appropriate and warns user that
there is misconfiguration on his side.

Add minimal sane kernel versions for architectures requiring that.

Also move (e)glibc-specific OLDEST_KERNEL variable from bitbake.conf to
(e)glibc.inc files that are more appropriate for this.

Acked-by: Tom Rini <trini@embeddedalley.com>