cxl: Fix timebase synchronization status on P9

cxl: Fix timebase synchronization status on P9

BugLink: https://bugs.launchpad.net/bugs/1757228
The PSL Timebase register is updated by the PSL to maintain the
timebase.

On P9, the Timebase value is only provided by the CAPP as received the
last time a timebase request was performed.

The timebase requests are initiated through the adapter configuration
or application registers.

The specific sysfs entry "/sys/class/cxl/cardxx/psl_timebase_synced"
is now dynamically updated according the content of the PSL Timebase
register.

Fixes: f24be42aab37 ("cxl: Add psl9 specific code")
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit c2be663d5307fb9751a562ac664fa78cd7a00e2b
 git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>