IMFS: Add fine grained configuration

Remove miniIMFS.  Statically initialize the root IMFS.

Add configuration options to disable individual
features of the root IMFS, e.g.
  o CONFIGURE_IMFS_DISABLE_CHOWN,
  o CONFIGURE_IMFS_DISABLE_FCHMOD,
  o CONFIGURE_IMFS_DISABLE_LINK,
  o CONFIGURE_IMFS_DISABLE_MKNOD,
  o CONFIGURE_IMFS_DISABLE_MOUNT,
  o CONFIGURE_IMFS_DISABLE_READLINK,
  o CONFIGURE_IMFS_DISABLE_RENAME,
  o CONFIGURE_IMFS_DISABLE_RMNOD,
  o CONFIGURE_IMFS_DISABLE_SYMLINK,
  o CONFIGURE_IMFS_DISABLE_UNMOUNT, and
  o CONFIGURE_IMFS_DISABLE_UTIME.

c/src/lib/libbsp/powerpc/beatnik/irq/irq_test_app.c

@@ -36,7 +36,6 @@ rtems_task Init(
 #define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
 #define CONFIGURE_MAXIMUM_TASKS            1
 #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
-#define CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM
 #include <confdefs.h>
 
 #include <stdio.h>