Fix rpm dependencies

Fix rpm dependencies

This change updates the rpm spec files to have strictly correct
package dependencies.  That means a few things:

* The zfs-modules package is now tied to a specific build of
  the spl-modules packages based on the kernel version.  This
  ensures that the correct spl-modules packages will always get
  installed and not just the newest.

* The zfs package now requires both the zfs-modules and spl
  packages.  Thus a 'yum install zfs' will pull in the minimal
  set of packages required for a functional system.

* The zfs-devel packages now require the zfs package to be
  installed which is normal behavior for -devel packages.

* Remove the redundant distribution release extension.  This
  is already added once because it is part of the kernel package
  release name.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>