msm: camera: isp: Fix the reset value of link_hdl

link_hdl is int32 variable. 0 is a valid value. So
in reset assign link_hdl to -1 instead of 0. Change
condition to check for valid values to >=0.

Change-Id: I2456dc77f68a4f289574ef1ebd0d2628f7c5a1d4
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>