cpuid.csv will be extended in further commits with all-publicly-known
CPUID leaves and bitfields.  Thus, modify has_subleafs() to identify all
known leaves with subleaves.

Remove the redundant "is_amd" check since all x86 vendors already report
the maxium supported extended leaf at leaf 0x80000000 EAX register.

The extra mentioned leaves are:

  - Leaf 0x12, Intel Software Guard Extensions (SGX) enumeration
  - Leaf 0x14, Intel process trace (PT) enumeration
  - Leaf 0x17, Intel SoC vendor attributes enumeration
  - Leaf 0x1b, Intel PCONFIG (Platform configuration) enumeration
  - Leaf 0x1d, Intel AMX (Advanced Matrix Extensions) tile information
  - Leaf 0x1f, Intel v2 extended topology enumeration
  - Leaf 0x23, Intel ArchPerfmonExt (Architectural PMU ext) enumeration
  - Leaf 0x80000020, AMD Platform QoS extended features enumeration
  - Leaf 0x80000026, AMD v2 extended topology enumeration

Set the 'max_subleaf' variable for all the newly marked leaves with extra
subleaves.  Ideally, this should be fetched from the CSV file instead,
but the current kcpuid code architecture has two runs: one run to
serially invoke the cpuid instructions and save all the output in-memory,
and one run to parse this in-memory output through the CSV specification.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240718134755.378115-7-darwi@linutronix.de