riscv: dts: microchip: remove pcie node from the sev kit

The SEV kit reference design does not hook up the PCIe root port to the
core complex including it is misleading.
The entry is a re-use mistake - I was not aware of this when I moved
the PCIe node out of mpfs.dtsi so that individual bistreams could
connect it to different fics etc.

The node is disabled, so there should be no functional change here.

Fixes: 978a17d1 ("riscv: dts: microchip: add sevkit device tree")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>