etherswitch: Stop checking for failures from malloc(M_WAITOK)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D45852
(cherry picked from commit 48741f4ceca71523aa1fa8da3bb78b184fad4aca)
(cherry picked from commit e78c315e8941ff39d89c45ffa5841b8028a3bbce)