LinuxKPI: device.h add devm_kmemdup()

Add devm_kmemdup() as needed by a networking driver.

Sponsored by: The FreeBSD Foundation
eviewed by: hselasky, emaste
Differential Revision: https://reviews.freebsd.org/D36652

(cherry picked from commit e999fbf0776208f9ecbc2926fd088427d766b014)