After a discussion mixed on mailing list and irc, it was agreed that
more abstraction for plugins is better (so developers don't have to add
a check to HAVE_DISK_STORAGE when writing disk-specific code)
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21923 a1c6a512-1295-4272-9138-f99709370657
storage_sleep, storage_spin, storage_spindown are only defined if #defiend (HAVE_DISK_STORAGE), not for MMC/ATA/SD
remove already unneeded nand_disk_is_active, nand_soft_reset
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21912 a1c6a512-1295-4272-9138-f99709370657