powerpc/pseries/htmdump: Fix the offset value used in processor configuration dump

powerpc/pseries/htmdump: Fix the offset value used in processor configuration dump

H_HTM call is invoked using three parameters specifying
the address of the buffer, size of the buffer and offset
where to read from. offset used was always zero.
"offset" is value from output buffer header that points
to next entry to dump. zero is the first entry to dump.
next entry is read from the output bufferbyte offset 0x8.
Update htminfo_read() function to use right offset. Return
when offset points to -1

Fixes: dea7384e14e7 ("powerpc/pseries/htmdump: Add htm info support to htmdump module")
Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260314132432.25581-2-atrajeev@linux.ibm.com