net: irda: set error code on failures

When the calls to kzalloc() fail, the value of return variable ret may
be 0. 0 means success in this context. This patch fixes the bug,
assigning "-ENOMEM" to ret before calling kzalloc().

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=188971

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>