drm/vmwgfx: fix memory leak when too many retries have occurred

Currently when too many retries have occurred there is a memory
leak on the allocation for reply on the error return path. Fix
this by kfree'ing reply before returning.

Addresses-Coverity: ("Resource leak")
Fixes: a9cd9c04

 ("drm/vmwgfx: Add a check to handle host message failure")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>
Signed-off-by: Deepak Rawat <drawat@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>