msm: ADSPRPC: Validate ADSP remote heap memory

Check for proper condition for remote heap not being initialized
before freeing the memory.

Change-Id: Icfba23fca02226724a7f171d7850a5fc7cef99d8
Acked-by: Bharath Kumar <bkumar@qti.qualcomm.com>
Acked-by: Vishnu Karthik <vikarthi@qti.qualcomm.com>
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>