drivers: disk: mmc_subsys: remove CONFIG_MMC_VOLUME_NAME

Remove CONFIG_MMC_VOLUME_NAME, and set the disk name based on the
``disk-name`` property. This aligns with other disk drivers, and allows
for multiple instances of the mmc_subsys disk driver to be registered.

Add disk-name properties for all in tree definitions for the
mmc-subsys disk driver, and change all in tree usage of the disk name

Fixes #75004

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>