davinci: DA850/OMAP-L138 EVM: implement autodetect of RMII PHY

Implement autodetection of RMII PHY by shifting the decision
to use the RMII PHY to da850_evm_ui_expander_setup() from
da850_evm_init() earlier.

Without this patch, selecting RMII PHY in the UI expander menu
will make the MII PHY unusable even though UI board is not
connected.

The actual configuration and registration of the EMAC device
is delayed to device_initcall() so it happens after the UI card
detection is complete.

A side effect of this patch is the removal of a voilation of
Documentation/SubmittingPatches section 2.2 in function
da850_evm_init()

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>