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

Signed-off-by: NDiana Craciun <diana.craciun@nxp.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Documentation/admin-guide/kernel-parameters.txt

@@ -2826,7 +2826,7 @@
 			check bypass). With this option data leaks are possible
 			in the system.
 
-	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.