carl9170: match wait_for_completion_timeout return type

Return type of wait_for_completion_timeout is unsigned long not int.
An appropriately named unsigned long is added, and the assignments
as well as error checking fixed up.

API conformance testing for completions with coccinelle spatches are being
used to locate API usage inconsistencies:
./drivers/net/wireless/ath/carl9170/usb.c:675
	int return assigned to unsigned long

Patch was compile tested with x86_64_defconfig + CONFIG_ATH_CARDS=m,
CONFIG_CARL9170=m

Patch is against 4.1-rc3 (localversion-next is -next-20150512)

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>