cxl/pci: Introduce cxl_request_irq()

Factor out common functionality/semantics for cxl shared interrupts
into a new helper on top of devm_request_irq().

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/r/20230523170927.20685-4-dave@stgolabs.net
Signed-off-by: Dan Williams <dan.j.williams@intel.com>