msm: pcie: correct exit code for invalid Root Complex indexes

In the case where the Root Complex fails to retrive a valid
index, the exit code fails to handle this correctly. This
change corrects the way the exit code handles invalid root
complex indexes.

Change-Id: Ie832fec1be2b05dea05b8917348a1c08cdc1d681
Signed-off-by: Tony Truong <truong@codeaurora.org>