ARM: dts: msm: Added uC memory region to IPA SRAM on SDM845

Since there is no dedicated descriptor RAM for uC in SDM845, the
uC event ring is added to IPA SRAM. The uC transfer ring is placed in
uC DRAM, since IPA only needs read access to it. However the uC event
ring cannot be placed in uC DRAM, since IPA needs to write to it and
this is forbidden per security policy. uC event ring get 1K space
from the bottom of the IPA SRAM allocation on account of the modem
memory region.

Change-Id: I87f2ca1a7e0572a86b8b79da05e15193d90249b9
Acked-by: Dmitry Kogan <dmitryk@qti.qualcomm.com>
Signed-off-by: Amir Levy <alevy@codeaurora.org>