staging: lustre: Fix address space mismatch in ksocknal_recv_iov()

This patch fixes the following sparse warnings:

drivers/staging/lustre/lnet/klnds/socklnd/socklnd_cb.c:284:51: warning:
	cast removes address space of expression
drivers/staging/lustre/lnet/klnds/socklnd/socklnd_cb.c:284:39: warning:
	incorrect type in assignment (different address spaces)
drivers/staging/lustre/lnet/klnds/socklnd/socklnd_cb.c:284:39:    expected
	void [noderef] <asn:1>*iov_base
drivers/staging/lustre/lnet/klnds/socklnd/socklnd_cb.c:284:39:    got
	void *<noident>

by simplifying an expression containing non-__user-attributed type names.

Signed-off-by: Artemiy Volkov <artemiyv@acm.org>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>