Use explicit ENOMEM when {m,re}alloc fails

Use explicit ENOMEM when {m,re}alloc fails

Currently our codebase has a mix of explicitly using ENOMEM and
propagating the errno... The latter of which is guaranteed to be ENOMEM
as documented in the manual pages.

Consolidate on ENOMEM, both for consistency sake and to remove a few
bytes off our binaries ;-)

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/368
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>