msm: isp: Make HALT independent from disable_camif

AXI should be halted whenever all HW streams are stopping. This will
improve KPI even for RDI streams. Currently halt is determined using
Disable_Camif which is only valid for PIX streams. Decouple the two to
improve KPI on RDI and avoid wait.
Also, cleanup after timeout in start_axi. Remove handling of SD_SHUTDOWN
to avoid multiple release.

Change-Id: I09db8adb766d2e7889443f779a716aaa2f6c09d1
Signed-off-by: Harsh Shah <harshs@codeaurora.org>