Fix sd-as3525.c build for non-multidrive targets
treefc7a6cd11236eefc5d2a0be4e8f06f7c298ee8da
drwxr-xr-x - apps
drwxr-xr-x - backdrops
drwxr-xr-x - bootloader
drwxr-xr-x - docs
drwxr-xr-x - firmware
drwxr-xr-x - flash
drwxr-xr-x - fonts
drwxr-xr-x - gdb
drwxr-xr-x - icons
drwxr-xr-x - lib
drwxr-xr-x - manual
drwxr-xr-x - rbutil
drwxr-xr-x - tools
drwxr-xr-x - uisimulator
drwxr-xr-x - utils
drwxr-xr-x - wps