powerpc/fsl: Add FSL_PPC_BOOK3E as supported arch for nospectre_v2 boot arg

BugLink: https://bugs.launchpad.net/bugs/1830176

commit e59f5bd7 upstream.
Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[juergh: Adjusted context.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

Documentation/kernel-parameters.txt

@@ -2606,7 +2606,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			nosmt=force: Force disable SMT, cannot be undone
 				     via the sysfs control file.
 
-	nospectre_v2	[X86] Disable all mitigations for the Spectre variant 2
+	nospectre_v2	[X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2
 			(indirect branch prediction) vulnerability. System may
 			allow data leaks with this option, which is equivalent
 			to spectre_v2=off.