cmd: CONFIG_CMD_BLOBLIST must depend on CONFIG_BLOBLIST

With CONFIG_CMD_BLOBLIST=y, CONFIG_BLOBLIST=n linker errors occur:

    usr/bin/ld: cmd/bloblist.o: in function `do_bloblist_list':
    cmd/bloblist.c:27:(.text.do_bloblist_list+0x6):
    undefined reference to `bloblist_show_list'

    /usr/bin/ld: cmd/bloblist.o: in function `do_bloblist_info':
    cmd/bloblist.c:19:(.text.do_bloblist_info+0x6):
    undefined reference to `bloblist_show_stats'

Fixes: 4aed2276 ("bloblist: Add a command")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>