Davinci 8xx: Move common functions to share code

As more Davinci 8xx board can be added, move common code
to be shared between boards.

 * rebased ontop of Sugosh's patches
 * moving the HAWKBOARD_KICK{0,1}_UNLOCK defines to
   arch/arm/include/asm/arch-davinci/davinci_misc.h from to
   arch/arm/include/asm/arch-davinci/da8xx_common.h
 * don't define dram functions in PRELOADER
 * move sync_env_enetaddr into existing EMAC ifdef
 * use misc.c in hawkboard nand_spl

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Signed-off-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>