fix(mt8188): add mmap entry for CPU idle SRAM

CPU PM driver accesses CPU idle SRAM during the system suspend
process. The region of CPU idle SRAM needs to be added as mmap entry.
Otherwise, the execption would occur.

BUG=b:244215539
TEST=Test of suspend resume passes.

Signed-off-by: Liju-Clr Chen <liju-clr.chen@mediatek.com>
Change-Id: I5838964fd9cb1b833e4006e2123febb4a4601003