memory: tegra210-emc: replace DEFINE_SIMPLE_ATTRIBUTE with DEFINE_DEBUGFS_ATTRIBUTE

Fix the following coccicheck warning:
  drivers/memory/tegra/tegra210-emc-core.c:1665:0-23:WARNING
    tegra210_emc_debug_min_rate_fops should be defined  with DEFINE_DEBUGFS_ATTRIBUTE

Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
Link: https://lore.kernel.org/r/20210825063739.70260-1-deng.changcheng@zte.com.cn


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>