davinci: cpu-specific build uses conditional make syntax

Update cpu/arm926ejs/davinci/Makefile to use COBJ-y type syntax.
Add the first conditional: for EMAC driver support.  Not all
chips have an EMAC; and boards might not use it, anyway.

This doesn't touch PHY configuration; that should eventually
become conditional too.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
1 file changed