cpufreq: Add boost_freq_req QoS request

cpufreq: Add boost_freq_req QoS request

The Power Management Quality of Service (PM QoS) allows to
aggregate constraints from multiple entities. It is currently
used to manage the min/max frequency of a given policy.

Frequency constraints can come for instance from:
 - Thermal framework: acpi_thermal_cpufreq_init()
 - Firmware: _PPC objects: acpi_processor_ppc_init()
 - User: by setting policyX/scaling_[min|max]_freq
The minimum of the max frequency constraints is used to compute
the resulting maximum allowed frequency.

When enabling boost frequencies, the same frequency request object
(policy->max_freq_req) as to handle requests from users is used.
As a result, when setting:
 - scaling_max_freq
 - boost
The last sysfs file used overwrites the request from the other
sysfs file.

To avoid this, create a per-policy boost_freq_req to save the boost
constraints instead of overwriting the last scaling_max_freq
constraint.

policy_set_boost() calls the cpufreq set_boost callback.
Update the newly added boost_freq_req request from there:
 - whenever boost is toggled
 - to cover all possible paths

In the existing .set_boost() callbacks:
 - Don't update policy->max as this is done through the qos notifier
   cpufreq_notifier_max() which calls cpufreq_set_policy().
 - Remove freq_qos_update_request() calls as the qos request is now
   done in policy_set_boost() and updates the new boost_freq_req

$ ## Init state
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

$ echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

$ echo 1 > ../boost
scaling_max_freq:1200000
cpuinfo_max_freq:1200000

$ echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

$ ## Final step:
$ ## Without the patches:
$ echo 0 > ../boost
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

$ ## With the patches:
$ echo 0 > ../boost
scaling_max_freq:800000
cpuinfo_max_freq:1000000

Note:
cpufreq_frequency_table_cpuinfo() updates policy->min
and max from:
A.
cpufreq_boost_set_sw()
\-cpufreq_frequency_table_cpuinfo()
B.
cpufreq_policy_online()
\-cpufreq_table_validate_and_sort()
  \-cpufreq_frequency_table_cpuinfo()
Keep these updates as some drivers expect policy->min and
max to be set through B.

Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20260326204404.1401849-3-pierre.gondois@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>