arm, davinci_emac: fix driver bug if more then 3 PHYs are detected

arm, davinci_emac: fix driver bug if more then 3 PHYs are detected

since commits:
davinci: emac: add support for more than 1 PHYs
062fe7d332c28ede25626f448681e43d76bb312e

davinci: remove obsolete macro CONFIG_EMAC_MDIO_PHY_NUM
fb1d6332b5430b90a8fa8ebab709f33a60e9f816

I get following warning on the enbw_cmc board:

Err:   serial
Net:    5 ETH PHY detected
miiphy_register: non unique device name 'KSZ8873 @ 0x01'
DaVinci-EMAC
Hit any key to stop autoboot:  0

Also I see some debug printfs:

=> run load
+ emac_close
+ emac_ch_teardown
- emac_ch_teardown
+ emac_ch_teardown
- emac_ch_teardown
- emac_close
+ emac_open
- emac_open
Using DaVinci-EMAC device

reason is 062fe7d332c28ede25626f448681e43d76bb312e new define MAX_PHY.
This is set to 3! I get on this board 5 active phys, so
this leads in wrong memory writes ...

so I changed:

- define CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT to set
  the MAX_PHY value, add a description in README
  for the new CONFIG_SYS option.
- print an error message if more then MAX_PHYs are
  detected.
- fill the active_phy_addr array in a for loop with
  0xff
- changed printf() in debug_emac()

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Manjunath Hadli <manjunath.hadli@ti.com>
Cc: Prabhakar Lad <prabhakar.csengg@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Tom Rini <tom.rini@gmail.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>