cpufreq: userspace: set CPUFREQ_GOV_STRICT_TARGET flag

cpufreq: userspace: set CPUFREQ_GOV_STRICT_TARGET flag

When the userspace governor is used, the user intends to set a fixed CPU
frequency for a policy, for whatever reason. The CPUFREQ_GOV_STRICT_TARGET
flag is the required behaviour. Without this flag, the intel_pstate driver,
with HWP enabled, will set HWP_MIN_PERF to the target frequency and
HWP_MAX_PERF to the policy maximum, when configuring the HWP_REQUEST MSR.

This lets the hardware choose any frequency between the target frequency
and the policy maximum, which is not the intended behaviour. To fix this,
`cat scaling_setspeed > scaling_max_freq` had to be done. With this patch,
that is no longer necessary. Setting scaling_setspeed is sufficient, as
expected.

Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
Link: https://patch.msgid.link/20250527-userspace-governor-doc-v2-1-0e22c69920f2@sony.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>