arm/dt: msm8974: Remove unused MPP configuration entries

The PMIC MPP5 pin is not wired to the SPI Ethernet
controller on MSM8974 MTP and FLUID targets, so an MPP
configuration entry for this feature is not required.

CRs-Fixed: 468869
Change-Id: I395de28f8462c183b65286d5d8c4a761ba27ab0f
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>