x86: Properly align interrupt vectors for MSI

MSI (not MSI-X) interrupt vectors must be allocated in groups that are
powers of 2, and the block of IDT vectors must be aligned to the size
of the request.

The code in native_apic_alloc_vectors() does an alignment check in the loop:

if ((vector & (align - 1)) != 0)
    continue;
first = vector;

But it adds APIC_IO_INTS to the value it returns:

return (first + APIC_IO_INTS);

The problem is that APIC_IO_INTS is not a multiple of 32. It is 48:

As a result, a request for 32 vectors (the max supported by MSI), was
not always aligned. To fix, check the alignment of
'vector + APIC_IO_INTS' in the loop.

PR: 274074
Reviewed by: jhb