powerpc/pseries/htmdump: Add htm info support to htmdump module

Support dumping system processor configuration from Hardware
Trace Macro (HTM) function via debugfs interface. Under
debugfs folder "/sys/kernel/debug/powerpc/htmdump", add
file "htminfo".

The interface allows only read of this file which will present the
content of HTM buffer from the hcall. The 16th offset of HTM
buffer has value for the number of entries for array of processors.
Use this information to copy data to the debugfs file

Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250420180844.53128-6-atrajeev@linux.ibm.com