HACK: memory: tegra: Do not go to 40.8 MHz EMC

BUG=chrome-os-partner:53415
TEST=system idle

Change-Id: I308fb44d063a860e40431c2b23b5a8639a1e3fad
Signed-off-by: Christopher Freeman <cfreeman@nvidia.com>
Reviewed-on: https://chromium-review.googlesource.com/345666
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
(cherry picked from commit eb429de82ed88f44b39387dc3dfd7c187dfb6a7b)
Reviewed-on: https://chromium-review.googlesource.com/359449
Commit-Queue: Stephen Barber <smbarber@chromium.org>

drivers/memory/tegra/tegra210-emc.c

@@ -1228,6 +1228,9 @@ static int find_matching_input(struct emc_table *table, struct emc_sel *sel)
 	unsigned long input_rate = 0;
 	struct clk *input_clk;
 
+	if (table->rate == 40800)
+		return -EINVAL;
+
 	div_value = emc_div_val(table->clk_src_emc);
 	src_value = emc_src_val(table->clk_src_emc);