Check /boot for free space

On the OC-SDP, check for adequate space in the /boot volume to upload the new boot image and bootloader. Use the show space boot command.
```
OC-SDP# show space boot
boot: 24759488/25760512 bytes (99%) remaining
```
You may delete files from an SFTP client if you need to free space.

The command check-space-remaining boot performs the same function as show space boot.