Documentation/ABI: ibm_rtl: The "What:" fields are incomplete

The "What:" field at the ABI should describe the location of
the ABI, e. g. the position under a mounted sysfs. However,
this file has only the basename without the path.

Fix it.

Cc: Vernon Mauery <vernux@us.ibm.com>
Cc: platform-driver-x86@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>