kvmtool: ARM: madvise mergeable and hugepage separately

The madvise behavior is not a bit field and hence can not be or'ed.
Also madvise_behavior_valid checks the flag using a case statement
hence only one behavior is supposed to be supplied. Call madvise
twice, once for MERGEABLE and once for HUGEPAGE.

Acked-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Will Deacon <will.deacon@arm.com>