dev, arm: Cleanup Pl050 interrupt handling

Add support for TX interrupts and cleanup existing RX interrupt
handling.

Change-Id: If2e5b0c0cc6fbeb2dce09e7e9d935647516b2c47
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sudhanshu Jha <sudhanshu.jha@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/9769
3 files changed