soc: qcom: smem_log: Check smem_alloc() return values

smem_alloc() is not guaranteed to succeed and may return error.  Smem_log
ignores any possible errors from smem_alloc().

Check the return value of smem_alloc() calls for errors and handle them as
necessary.

CRs-Fixed: 630076
Change-Id: I71b77a8f878ee8e3f21ad2c38c466dc426594c1c
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>