vmw_balloon: Split refused pages

The hypervisor might refuse to inflate pages. While the balloon driver
handles this scenario correctly, a refusal to inflate a 2MB pages might
cause the same page to be allocated again later just for its inflation
to be refused again. This wastes energy and time.

To avoid this situation, split the 2MB page to 4KB pages, and then try
to inflate each one individually. Most of the 4KB pages out of the 2MB
should be inflated successfully, and the balloon is likely to prevent
the scenario of repeated refused inflation.

Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>