soc: qcom: sysmon-qmi: Fix max qmi msg length

Add enum for the max qmi msg length in the SSCTL interface. Use this
size in qmi handle init so messages are not truncated. Zero initialize
the response buffer to prevent extra data after qmi decodes the error
response string.

Also, the error-response can contain multiple string prefixes. Hence,
prevent comparing with "ssr:return:" format.

Change-Id: Ieb4c67050448a9ae7789155b7fcbafd727adef59
Signed-off-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>