powerpc: Disable CPU_FTR_TM if TM is disabled by firmware

Firmware is allowed to communicate to us via the "ibm,pa-features" property
that TM (Transactional Memory) support is disabled.

Currently this doesn't happen on any platform we're aware of, but we should
honor it anyway.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/prom.c

@@ -160,6 +160,12 @@ static struct ibm_pa_feature {
 	{CPU_FTR_NODSISRALIGN, 0, 0,	1, 1, 1},
 	{0, MMU_FTR_CI_LARGE_PAGE, 0,	1, 2, 0},
 	{CPU_FTR_REAL_LE, PPC_FEATURE_TRUE_LE, 5, 0, 0},
+	/*
+	 * If the kernel doesn't support TM (ie. CONFIG_PPC_TRANSACTIONAL_MEM=n),
+	 * we don't want to turn on CPU_FTR_TM here, so we use CPU_FTR_TM_COMP
+	 * which is 0 if the kernel doesn't support TM.
+	 */
+	{CPU_FTR_TM_COMP, 0, 0,		22, 0, 0},
 };
 
 static void __init scan_features(unsigned long node, const unsigned char *ftrs,