linux.inc: remove the obsolete linux.inc kernel recipe include
linux.inc was used by older kernel recipes which have now been removed from the
core meta data. I references machines now only defined in meta-extras. The
configure prepend mangles the kernel .config in non-intuitive ways and the
install peroforms some odd boot image manipulation that is not used nor required
by supported machines. The required functionality, such as defconfig setup, has
already been moved to the kernel bbclass. Remove linux.inc to avoid confusion
for new kernel recipe authors and clean up the kernel meta data.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
