cxl: Workaround XSL bug that does not clear the RA bit after a reset

An issue was noted in our debug logs where the XSL would leave the RA
bit asserted after an AFU reset operation, which would effectively
prevent further AFU reset operations from working.

Workaround the issue by clearing the RA bit with an MMIO write if it is
still asserted after any AFU control operation.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>