ACPI: CPPC: Detect preferred core availability on online CPUs

Commit 279f838 ("x86/amd: Detect preferred cores in
amd_get_boost_ratio_numerator()") introduced the ability to detect the
preferred core on AMD platforms by checking if there at least two
distinct highest_perf values.

However, it uses for_each_present_cpu() to iterate through all the
CPUs in the platform, which is problematic when the kernel is booted
with "nosmt=force" commandline option.

Hence limit the search to only the online CPUs.

Fixes: 279f838 ("x86/amd: Detect preferred cores in amd_get_boost_ratio_numerator()")
Reported-by: Christopher Harris <chris.harris79@gmail.com>
Closes: https://lore.kernel.org/lkml/CAM+eXpdDT7KjLV0AxEwOLkSJ2QtrsvGvjA2cCHvt1d0k2_C4Cw@mail.gmail.com/
Reviewed-by: "Mario Limonciello (AMD) (kernel.org)" <superm1@kernel.org>
Tested-by: Chrisopher Harris <chris.harris79@gmail.com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://patch.msgid.link/20251107074145.2340-2-gautham.shenoy@amd.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: gautshen

arch/x86/kernel/acpi/cppc.c

@@ -196,7 +196,7 @@ int amd_detect_prefcore(bool *detected)
 		break;
 	}
 
-	for_each_present_cpu(cpu) {
+	for_each_online_cpu(cpu) {
 		u32 tmp;
 		int ret;