drm/radeon: Fix comment typo

The double `have' is duplicated in line 696, remove one.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_gem.c

@@ -693,7 +693,7 @@ int radeon_gem_va_ioctl(struct drm_device *dev, void *data,
 	}
 
 	/* !! DONT REMOVE !!
-	 * We don't support vm_id yet, to be sure we don't have have broken
+	 * We don't support vm_id yet, to be sure we don't have broken
 	 * userspace, reject anyone trying to use non 0 value thus moving
 	 * forward we can use those fields without breaking existant userspace
 	 */