Documentation: Add nospectre_v1 parameter

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

Documentation/admin-guide/kernel-parameters.txt

@@ -2687,6 +2687,10 @@
 	nosmt		[KNL,S390] Disable symmetric multithreading (SMT).
 			Equivalent to smt=1.
 
+	nospectre_v1	[PPC] Disable mitigations for Spectre Variant 1 (bounds
+			check bypass). With this option data leaks are possible
+			in the system.
+
 	nospectre_v2	[X86] Disable all mitigations for the Spectre variant 2
 			(indirect branch prediction) vulnerability. System may
 			allow data leaks with this option, which is equivalent