Staging: ipack/bridges/tpci200: Remove side effects of tpci200_{request,free}_irq.

Use the __tpci200_{set,clear}_mask routines to access control
register.  Do not overwrite flags unrelated to interrupt handling.

Signed-off-by: Jens Taprogge <jens.taprogge@taprogge.org>
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>