spi: sh-msiof: drop unneeded MODULE_ALIAS

The MODULE_DEVICE_TABLE already creates proper alias for platform
driver.  Having another MODULE_ALIAS causes the alias to be duplicated.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210916164423.134603-2-krzysztof.kozlowski@canonical.com
Signed-off-by: Mark Brown <broonie@kernel.org>