Process negative return values from intf->probe()

Some platforms use probe methods that may encounter errors, such as
missing device tree files.

BUG=none
BRANCH=none
TEST=peach no longer detected if /proc/device-tree/model not found
(probe method returns -1)

Change-Id: I8dbe4f6a1e0d382afdf962476cc24c05b1cdf3d5
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/219576
Reviewed-by: Shawn Nematbakhsh <shawnn@chromium.org>
1 file changed