octeontx2-af: debugfs: fix error return of allocations

Current memory failure code in the debugfs returns -ENOSPC. This is
normally used for indicating that there is no space left on the
device and is not applicable for memory allocation failures.
Replace this with -ENOMEM.

Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Link: https://lore.kernel.org/r/20220430194656.44357-1-dossche.niels@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>