gpu/trace: Minor comment updates for gpu_mem_total tracepoint

This change updates the improper comment for the 'size' attribute in the
tracepoint definition. Most gfx drivers pre-fault in physical pages
instead of making virtual allocations. So we drop the 'Virtual' keyword
here and leave this to the implementations.

Link: http://lkml.kernel.org/r/20200428220825.169606-1-zzyiwei@google.com

Signed-off-by: Yiwei Zhang <zzyiwei@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/trace/events/gpu_mem.h

@@ -24,7 +24,7 @@
  *
  * @pid: Put 0 for global total, while positive pid for process total.
  *
- * @size: Virtual size of the allocation in bytes.
+ * @size: Size of the allocation in bytes.
  *
  */
 TRACE_EVENT(gpu_mem_total,