Add a simplified path evaluation function IMFS_eval_path_devfs() for a
device only IMFS configuration.
The code size can be further reduced by the application if it disables
the support for legacy IO drivers via:
#define CONFIGURE_IMFS_DISABLE_MKNOD
#define CONFIGURE_IMFS_DISABLE_MKNOD_DEVICE
Obsolete CONFIGURE_MAXIMUM_DEVICES. Remove BSP_MAXIMUM_DEVICES.
Update #3894.
Update #3898.
0161b93d50