Only align MSI message groups based on the number of messages being allocated, not the maximum number of messages the device supports.  The spec only requires the former, and I believe I implemented the latter due to misunderstanding an e-mail.  In particular, this fixes an issue where having several devices that all support 16 messages can run out of IDT vectors on x86 even though the driver only uses a single message.
Only align MSI message groups based on the number of messages being
allocated, not the maximum number of messages the device supports.  The
spec only requires the former, and I believe I implemented the latter due
to misunderstanding an e-mail.  In particular, this fixes an issue where
having several devices that all support 16 messages can run out of
IDT vectors on x86 even though the driver only uses a single message.

Submitted by:	Bret Ketchum  bcketchum of gmail
MFC after:	1 week

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