x86/CPU/AMD: Print the reason for the last reset

The following register contains bits that indicate the cause for the
previous reset.

  PMx000000C0 (FCH::PM::S5_RESET_STATUS)

This is useful for debug. The reasons for reset are broken into 6 high level
categories. Decode it by category and print during boot.

Specifics within a category are split off into debugging documentation.

The register is accessed indirectly through a "PM" port in the FCH. Use
MMIO access in order to avoid restrictions with legacy port access.

Use a late_initcall() to ensure that MMIO has been set up before trying to
access the register.

This register was introduced with AMD Family 17h, so avoid access on older
families. There is no CPUID feature bit for this register.

  [ bp: Simplify the reason dumping loop.
    - merge a fix to not access an array element after the last one:
      https://lore.kernel.org/r/20250505133609.83933-1-superm1@kernel.org


      Reported-by: James Dutton <james.dutton@gmail.com>
      ]

  [ mingo:
    - Use consistent .rst formatting
    - Fix 'Sleep' class field to 'ACPI-State'
    - Standardize pin messages around the 'tripped' verbiage
    - Remove reference to ring-buffer printing & simplify the wording
    - Use curly braces for multi-line conditional statements ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250422234830.2840784-6-superm1@kernel.org