rhel: Fix dual kernel rpm install for RHEL 8.4

RHEL 8.4 is the first of the RHEL 8.x kernels that has broken ABI so
it requires the same sort of fix as we did for several RHEL 7.x kernel
that needed two kernel rpms to work for all minor revisions of the
baseline kernel module.

Signed-off-by: Greg Rose <gvrose8192@gmail.com>

rhel/usr_share_openvswitch_scripts_ovs-kmod-manage.sh

@@ -24,6 +24,7 @@
 #   - 3.10.0 major revision 1160 (RHEL 7.9)
 #   - 4.4.x,  x >= 73           (SLES 12 SP3)
 #   - 4.12.x, x >= 14           (SLES 12 SP4).
+#   - 4.18.x major revision 305  (RHEL 8.4)
 # It is packaged in the openvswitch kmod RPM and run in the post-install
 # scripts.
 #
@@ -139,6 +140,13 @@ elif [ "$mainline_major" = "4" ] && [ "$mainline_minor" = "12" ]; then
         ver_offset=2
         installed_ver="$mainline_patch"
     fi
+elif [ "$mainline_major" = "4" ] && [ "$mainline_minor" = "18" ]; then
+    if [ "$major_rev" = "305" ]; then
+        echo "rhel84"
+        comp_ver=9
+        ver_offset=4
+        installed_ver="$minor_rev"
+    fi
 fi
 
 if [ X"$ver_offset" = X ]; then