ARM: i.MX: Remove Phytec i.MX27 PCM038/PCM970 board files

pcm970-baseboard.c and mach-pcm038.c can be replaced with their
devicetree equivalents: imx27-phytec-phycore-rdk.dts and
imx27-phytec-phycore-som.dtsi respectively, so remove the board files.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>