memory: tegra20-emc: Correct memory device mask

Memory chip select is swapped when we read mode register, correct it.
We didn't have devices that use a single LPDDR chip and both chips are
always identical, hence this change is just a minor improvement.

Fixes: 131dd9a4 ("memory: tegra20-emc: Support matching timings by LPDDR2 configuration")
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20211222043215.28237-2-digetx@gmail.comSigned-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

drivers/memory/tegra/tegra20-emc.c

@@ -540,7 +540,7 @@ static int emc_read_lpddr_mode_register(struct tegra_emc *emc,
 					unsigned int register_addr,
 					unsigned int *register_data)
 {
-	u32 memory_dev = emem_dev + 1;
+	u32 memory_dev = emem_dev ? 1 : 2;
 	u32 val, mr_mask = 0xff;
 	int err;