mips: ci20: Add external memory controller to defconfig

The dm9000 ethernet chip on the ci20 is connected via the NAND &
external memory controller (NEMC) of the jz4780. The driver is not
enabled by ci20_defconfig. Hence ethernet seems to not work by default.
This patch enables the NEMC driver in ci20_defconfig.

[paul.burton@imgtec.com: Clarified commit message slightly.]

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
dm9000: Add regulator and reset support to dm9000

In boards, the dm9000 chip's power and reset can be controlled by gpio.

It makes sense to add them to the dm9000 driver and let dt be used to
enable power and reset the phy.

[paul.burton@imgtec.com: s/dev_dgb/dev_dbg/]

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
mips: ci20: Add ethernet regulator node to dt

The ethernet regulator is a simple fixed gpio regulator.
Add node to dt.

[paul.burton@imgtec.com: Dropped extaneous newline.]

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
dt: ci20: dm9000: move ethernet node under nemc

Ethernet on the ci20 is via the dm9000 chip which is connected via nemc.

Put the dm9000 node under nemc with optimized timings.
Checked using iperf.
Downstream ~70Mbps. Upstream at 45Mbps. With optimized timings.
Downstream was around 30Mbps with default NAND timings in driver code.

[paul.burton@imgtec.com: Dropped extaneous newline.]

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>