vmw_balloon: simplify vmballoon_send_get_target()

vmw_balloon: simplify vmballoon_send_get_target()

As we want to leave as little as possible on the global balloon
structure, to avoid possible future races, we want to get rid sysinfo.
We can actually get the total_ram directly, and simplify the logic of
vmballoon_send_get_target() a little.

While we are doing that, let's return int and avoid mistakes due to
bool/int conversions.

Reviewed-by: Xavier Deguillard <[email protected]>
Signed-off-by: Nadav Amit <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>