soc: qcom: pil: Avoid possible buffer overflow

MBA image size comparison check is currently being
done with a signed count whose value can possibly be
negative. If count value is negative then comparison
will always succeed and invoke memcpy with incorrect
value of count leading to buffer overflow. Fix this
by not using signed comparison.

Change-Id: Id2d0cafae01f940f36cfd559d4656fc0f022d6a5
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>