intel_idle: Add cmdline option to adjust C-states table

intel_idle: Add cmdline option to adjust C-states table

Add a new module parameter that allows adjusting the C-states table used by
the driver.

Currently, the C-states table is hardcoded in the driver based on the CPU
model. The goal is to have good enough defaults for most users.

However, C-state characteristics, such as exit latency and residency, can
vary between different variants of the same CPU model and BIOS settings.
Moreover, different platform usage models and user preferences may benefit
from different C-state target_residency values.

Provide a way for users to adjust the C-states table via a module parameter
"table". The general format is:
"state1:latency1:target_residency1,state2:latency2:target_residency2,..."

In other words, represent each C-state by its name, exit latency (in
microseconds), and target residency (in microseconds), separated by colons.
Separate multiple C-states by commas.

For example, suppose a CPU has 3 C-states with the following
characteristics:
  C1:  exit_latency=1, target_residency=2
  C1E: exit_latency=10, target_residency=10
  C6:  exit_latency=100, target_residency=500

Users can specify a custom C-states table as follows:

1. intel_idle.table="C1:2:2,C1E:5:20,C6:150:600"
   Result: C1:  exit_latency=2, target_residency=2
           C1E: exit_latency=5, target_residency=20
           C6:  exit_latency=150, target_residency=600
2. intel_idle.table="C6::400"
   Result: C1:  exit_latency=1, target_residency=2 (unchanged)
           C1E: exit_latency=10, target_residency=10 (unchanged)
           C6:  exit_latency=100, target_residency=400
                (only target_residency changed)

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20251216080402.156988-3-dedekind1@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>