libertas: changed some occurences of kmalloc() + memset(&a, 0, sz) to kzalloc()

[Holger Schurig]

The subject says it all.

Signed-off-by: Holger Schurig <hs4233 at mail.mn-solutions.de>

http://git.infradead.org/?p=users/schurig/libertas-cleanups-2.6.git;a=commitdiff;h=a4bcd412b938ebffd49d83e9692d101f8db6ac18