qemu-xen-trad/pt_msi_disable: do not clear all MSI flags

qemu-xen-trad/pt_msi_disable: do not clear all MSI flags

"qemu-xen-trad: fix msi_translate with PV event delivery" added a
pt_msi_disable() call into pt_msgctrl_reg_write, clearing the MSI flags
as a consequence. MSIs get enabled again soon after by calling
pt_msi_setup.

However the MSI flags are only setup once in the pt_msgctrl_reg_init
function, so from the QEMU point of view the device has lost some
important properties, like for example PCI_MSI_FLAGS_64BIT.

This patch fixes the bug by clearing only the MSI
enabled/mapped/initialized flags in pt_msi_disable.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Tested-by: G.R. <firemeteor@users.sourceforge.net>
Xen-devel: http://marc.info/?l=xen-devel&m=135489879503075