[SYCL] minor uninitialized value (#14403)

uninitialized value causing complaint from c.v.

Author: cperkinsintel

sycl/source/detail/event_impl.hpp

@@ -381,7 +381,7 @@ class event_impl {
   // If this event represents a submission to a
   // sycl::detail::pi::PiExtCommandBuffer the sync point for that submission is
   // stored here.
-  sycl::detail::pi::PiExtSyncPoint MSyncPoint;
+  sycl::detail::pi::PiExtSyncPoint MSyncPoint = 0;
 
   // If this event represents a submission to a
   // sycl::detail::pi::PiExtCommandBuffer the command-buffer command