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

Add htm setup support to htmdump module. To use the
HTM (Hardware Trace Macro), HTM buffer has to be allocated.
Support setup of HTM buffers via debugfs interface. Under
debugfs folder, "/sys/kernel/debug/powerpc/htmdump", add file
"htmsetup". The interface allows setup of HTM buffer by writing
size of HTM buffer in power of 2 to the "htmsetup" 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/20250420180844.53128-7-atrajeev@linux.ibm.com