memory: tegra20-emc: Correct memory device mask

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: 131dd9a436d8 ("memory: tegra20-emc: Support matching timings by LPDDR2 configuration")
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20211222043215.28237-2-digetx@gmail.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>