Fix nvmm_ram_block_added() function arguments

A parameter max_size was added to the RAMBlockNotifier
ram_block_added function. Use the max_size for pre allocation
of hva space.

Signed-off-by: Reinoud Zandijk <Reinoud@NetBSD.org>
Message-Id: <20210718134650.1191-3-reinoud@NetBSD.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>