soc: qcom: bam_dmux: Skip disconnect call on bootup

Added a flag to skip disconnect_to_bam call on modem
bootup. This would happen in scenarios when we haven't
received a powerdown request after the previous
reconnect_to_bam call or if the previous
reconnect_to_bam call has been skipped due to SSR.

Change-Id: Ia6f87be7a3a92c1b2d24b948e7012e3a128feb99
Signed-off-by: Vivek Golani <vgolani@codeaurora.org>