target/hppa: Implement do_transaction_failed handler for I/O errors

Add the do_transaction_failed() handler to tigger a HPMC to the CPU
in case of I/O transaction errors.

This is a preparation commit.
We still lack implementation for some registers, so do not yet enable sending
HPMCs.  Having this hunk here now nevertheless helps for the further
development, so that it can easily be enabled later on.

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