thunderbolt: Handle ring interrupt by reading interrupt status register

thunderbolt: Handle ring interrupt by reading interrupt status register

As per USB4 specification by default "Disable ISR Auto-Clear" bit is set
to zero and the Tx/Rx ring interrupt status needs to be cleared.

Hence handle it by reading the interrupt status register (ISR) in the
MSI-X handler.

Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>