hvmloader: reduce minimum allocation alignment from 1024 bytes to 16.

hvmloader: reduce minimum allocation alignment from 1024 bytes to 16.

1024 bytes create a lot of wastage when the majority of allocations
are of BIOS table data structures which are generally happy with much
lower alignment. I conservatively chose 16 bytes.

Most callers pass 0 for the alignment anyway, for the rombios high
code allocation I kept it 1024 byte aligned since it was the only case
that didn't seem obviously ok with a smaller alignment.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>