util: use memset() to initialize surface, sampler_view templates

util: use memset() to initialize surface, sampler_view templates

These initialization functions weren't initializing all the fields so
some had undefined values.  The callers of these functions sometimes use
a structure assignment to initialize new objects from these templates
so we'd just propagate the undefined values.  That made for some confusing
info when debugging, plus it could lead to bugs.

v2: fix surf pointer mix-up: "&surf" -> "surf"

Jakob Bornecrantz <jakob@vmware.com>