cpufreq: ACPI: Fix max-frequency computation

Commit 3c55e94c ("cpufreq: ACPI: Extend frequency tables to cover
boost frequencies") introduced an assumption in acpi_cpufreq_cpu_init()
that the first entry in the P-state table was the nominal frequency.
This assumption is incorrect. The frequency corresponding to the P0
P-State need not be the same as the nominal frequency advertised via
CPPC.

Since the driver is using the CPPC.highest_perf and CPPC.nominal_perf
to compute the boost-ratio, it makes sense to use CPPC.nominal_freq to
compute the max-frequency. CPPC.nominal_freq is advertised on
platforms supporting CPPC revisions 3 or higher.

Hence, fallback to using the first entry in the P-State table only on
platforms that do not advertise CPPC.nominal_freq.

Fixes: 3c55e94c ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20250113044107.566-1-gautham.shenoy@amd.com


[ rjw: Retain reverse X-mas tree ordering of local variable declarations ]
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>