soc: qcom: bgrsb: Enable command is processed only after BG UP.

Enable command can not be processed until BG is UP and
RSB configured. If Enable command is received before BG UP,
It is ignored and retried again by client.

Change-Id: I4f29eebd1db302213bded4fdafcec6a1843f8f88
Signed-off-by: Arjun Singh <arsingh@codeaurora.org>
Signed-off-by: Indrasena Reddy G <gisena@codeaurora.org>
Signed-off-by: Ajit Kumar <kajit@codeaurora.org>