ARM: dts: porter: Name serial port pfc subnode after device name

Name the Pin Function Controller subnode for SCIF0 after its device
name, instead of after the serial port alias.

This avoids conflicts when enabling support for more serial ports later,
either here or in a DT overlay.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>