IRQ: u16 is too narrow for an event channel number

IRQ: u16 is too narrow for an event channel number

FIFO event channels allow ports up to 2^17, so we need to use a wider
field in struct pirq. Move "masked" such that it may share the 8-byte
slot with struct arch_pirq on 64-bit arches, rather than leaving a
7-byte hole in all cases.

Take the opportunity and also add a comment regarding "arch" placement
within the structure.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Arm: fix build after 892b9dcebdb7

"IRQ: u16 is too narrow for an event channel number" introduced a use of
evetchn_port_t, but its typedef apparently surfaces indirectly here only
on x86.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 892b9dcebdb7f646657e11cfdd95a385107bbefa
master date: 2020-01-14 12:03:47 +0100
master commit: b4194711ffaffa5e63d986338fb8d4020fa6bad1
master date: 2020-01-14 16:06:27 +0100