am437x: Add am57xx_evm_defconfig using CONFIG_DM

Import various DT files for am57xx-beagle-x15 from
Linux Kernel v4.2
Add config file for this board, enable DM, DM_GPIO,
DM_SERIAL and DM_MMC.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
3 files changed