ARM: dts: msm: Enable memory allocation for diag on cobalt

The new diag client requires additional memory from hlos. This
patch caters to diag memory requirement.

CRs-Fixed: 1079523
Change-Id: Ia291140cd815589caca0eec5ab280961891ba064
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>