config: Enable the config CONFIG_MMC_SPEED_MODE_SET

config: Enable the config CONFIG_MMC_SPEED_MODE_SET

Enable setting speed mode using mmc dev commands.
The speed mode is provided as the last argument in these commands
(ex: mmc dev 0 0 10) and is indicated using the index from enum
bus_mode in include/mmc.h. A speed mode can be set if it is enabled
from device tree or from capabilities register

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20240708091755.5021-1-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>