sh: update r2d defconfig

- Disable CONFIG_SH_DMA to avoid boot up freeze on R2D-1
- Disable CONFIG_SH_STANDARD_BIOS to support R2D-PLUS boot loaders

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>