Update default stop-state-disable mask to cut only stop11

Stability improvements in microcode for stop4/stop5 are
available in upstream hcode images. Stop4 and stop5 can
be safely enabled by default.

Use ~0xE0000000 to cut all but stop0,1,2 in case there
are any issues with stop4/5.

example:
nvram -p ibm,skiboot --update-config opal-stop-state-disable-mask=0x1FFFFFFF

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

hw/slw.c

@@ -851,7 +851,7 @@ void add_cpu_idle_state_properties(void)
 	u64 *pm_ctrl_reg_val_buf;
 	u64 *pm_ctrl_reg_mask_buf;
 	u32 supported_states_mask;
-	u32 opal_disabled_states_mask = ~0xE0000000; /* all but stop0,1,2 */
+	u32 opal_disabled_states_mask = ~0xEC000000; /* all but stop11 */
 	const char* nvram_disable_str;
 	u32 nvram_disabled_states_mask = 0x00;
 	u32 stop_levels;