parisc: Clean up cpu_check_affinity() and drop cpu_set_affinity_irq()

The cpu_set_affinity_irq() isn't needed. Not the CPU irqs need to
change, but the slave irq chips simply need to be reprogrammed to
a new CPU irq with the txn_* functions.

Signed-off-by: Helge Deller <deller@gmx.de>