LU-6912 lnet: rework autoconf rules for external OFED

LU-6912 lnet: rework autoconf rules for external OFED

Remove extra checks for OFED development headers location because of
issue on Ubuntu.

Check for O2IBPATH/include/linux/compat_autoconf.h in modern OFEDs and
automatically generate CONFIG_COMPAT_RHEL_*_* for RHEL distributive if
it absent.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I6d21266bceca61504c0cca2d981f55ba22a85451
Reviewed-on: http://review.whamcloud.com/15811
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>