kernel.bbclass, module.bbclass: Make update-modules optional

kernel.bbclass, module.bbclass: Make update-modules optional

The update-modules mechanism is something of a historical relic and it isn't
entirely clear that it has a great deal of value nowadays.  Also, it causes a
problem when building a read-only rootfs since update-modules itself refuses
to configure offline.

Allow DISTROs to circumvent this whole thing by declaring (via DISTRO_FEATURES)
that they don't wish to use update-modules.  This is backfilled for existing
distributions and will have to be marked as CONSIDERED by those who actually
don't want it.

(From OE-Core rev: 14bf8ed115453077b4d4042b4b70ed6b3bca2a9f)

Signed-off-by: Phil Blundell <pb@pbcl.net>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>