soc: qcom: mem-buf: Fix message queue registration check

The condition that determines if we print an error after
failing to register for the mem-buf message queue checks
the return code against EPROBE_DEFER. This is not correct, as
error codes are negative, so fix the check.

Change-Id: I4ed03bde56c6edf66e0ffed060ec23a87a46be54
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>