soc: qcom: spss_utils: Modify memory unmapping

scheme for cmac_mem

IAR maps cmac_mem once and assumes it is mapped
from this moment onward. Therefore, move the
the call to iounmap(cmac_mem) to the remove() function.

Change-Id: I5afa3de900e4766520c106882e2485d6c335c54d
Signed-off-by: Nurit Lichtenstein <nuritl@codeaurora.org>