usnic: correctly handle kzalloc return value
usnic: correctly handle kzalloc return value

Since kzalloc returns memory address, not error code,
it should be checked whether it is null or not.

Signed-off-by: Insu Yun <e189e0339ff175cb87102353f9f5280f5ec6332b@gmail.com>
Reviewed-by: Dave Goodell <de01adc2b508aeef8d54b0f93219b552fee4eec0@cisco.com>
Signed-off-by: Doug Ledford <f35204f44eabfe97bbcdd18aee9e9fffc59f29e1@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs