Documentation: ioctl-number: Correct full path to papr-physical-attestation.h

Documentation: ioctl-number: Correct full path to papr-physical-attestation.h

Commit 03c9d1a5a30d93 ("Documentation: Fix description format for
powerpc RTAS ioctls") fixes Sphinx warning by chopping arch/ path
component of papr-physical-attestation.h to fit existing "Include File"
column. Now that the column has been widened just enough for that
header file, add back its arch/ path component.

Reviewed-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250714015711.14525-4-bagasdotme@gmail.com