Linux: use an int pointer for the size argument to getsockopt

Linux: use an int pointer for the size argument to getsockopt

getsockopt expects an int pointer as the size parameter, both in
the kernel version and our replacement compat inline function, which
causes warnings because we give it a size_t pointer.

Use an int variable instead.

Change-Id: Ide77ac01610c2f32f87d833c0d130c79007a1a33
Reviewed-on: http://gerrit.openafs.org/2417
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>