Enable QAT support in zfs-dkms RPM

Enable QAT accelerated gzip compression in zfs-dkms RPM package when
environment variant ICP_ROOT is set to QAT drive source code folder
and QAT hardware presence.  Otherwise, use default gzip compression.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: David Qian <david.qian@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #6932

scripts/dkms.mkconf

@@ -30,6 +30,12 @@ PRE_BUILD="configure
   --with-spl=\${source_tree}/spl-\${PACKAGE_VERSION}
   --with-spl-obj=\${dkms_tree}/spl/\${PACKAGE_VERSION}/\${kernelver}/\${arch}
   --with-spl-timeout=300
+  \$(
+    [[ -n \"\${ICP_ROOT}\" ]] && \\
+    {
+      echo --with-qat=\"\${ICP_ROOT}\"
+    }
+  )
   \$(
     [[ -r \${PACKAGE_CONFIG} ]] \\
     && source \${PACKAGE_CONFIG} \\