xen/balloon: Remove pr_info's and don't alter retry_count

In the past the retry_count (in other form of this code) was zero.
Meaning retry forever. Do the same thing here without changing it to
the value 16.

Also remove some of the pr_info as there is no need to spam
the user.

Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>