ARM: dts: msm: Update the ceiling / floor limits for GFX on 8953

To support the new fusing scheme, the ceiling and floor limits
for the GFX LDO modes have changed. Update them.

CRs-Fixed: 989270
Change-Id: Id1b71faf8b17b5bf83251fd45c3e7f37b487c6de
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>