ARM: dts: msm: Correct dump size of rpmh for sdxpoorwills

The original dump size of rpmh is unable to allocated. Correct
the size of rpmh to make SDI be able to dump rpmh.

CRs-Fixed: 2238517
Change-Id: I10ce6144b85047a583497b0d18fca4c102de5788
Signed-off-by: Mao Jinlong <jinlmao@codeaurora.org>