soc: qcom: bgrsb: Increase time out for RSB channel opening

Increases the required timeout for RSB channel opening as in BG ssr
event re-open may take more than existing time out.

Change-Id: Ibb20a55eef033fc51d567343798a0f5dbf00ca4e
Signed-off-by: Arjun Singh <arsingh@codeaurora.org>