tools/power/x86/intel-speed-select: Read TRL from mailbox

When SST-PP feature is not present, the TRL (Turbo Ratio Limits)
is read from MSRs. This is done as the mailbox command will fail
on Skylake-X based platform. But for IceLake servers, mailbox
commands can still be used. So add a check to allow for non Skylake
based platforms to read from mail box commands.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/platform-driver-x86/57d6648282491906e0e1f70fe3b9a44f72cec90d.camel@intel.com/Signed-off-by: Hans de Goede <hdegoede@redhat.com>

tools/power/x86/intel-speed-select/isst-core.c

@@ -804,7 +804,7 @@ int isst_get_process_ctdp(int cpu, int tdp_level, struct isst_pkg_ctdp *pkg_dev)
 				return ret;
 		}
 
-		if (!pkg_dev->enabled) {
+		if (!pkg_dev->enabled && is_skx_based_platform()) {
 			int freq;
 
 			freq = get_cpufreq_base_freq(cpu);

tools/power/x86/intel-speed-select/isst.h

@@ -255,4 +255,5 @@ extern int is_clx_n_platform(void);
 extern int get_cpufreq_base_freq(int cpu);
 extern int isst_read_pm_config(int cpu, int *cp_state, int *cp_cap);
 extern void isst_display_error_info_message(int error, char *msg, int arg_valid, int arg);
+extern int is_skx_based_platform(void);
 #endif