Staging: pohmelfs: net.c: include vmalloc.h

on Sparc64:
drivers/staging/pohmelfs/net.c:33: error: implicit declaration of function 'vmalloc'
drivers/staging/pohmelfs/net.c:42: error: implicit declaration of function 'vfree'

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>