board: ti: beagle_x15: Rename to indicate support for TI am57xx evms

board: ti: beagle_x15: Rename to indicate support for TI am57xx evms

BeagleBoard X15 (http://beagleboard.org/x15) support in u-boot does
actually support two different platform configuration offered by
TI. In addition to BeagleBoard X15, it also supports the TMDXEVM5728
(or more commonly known as AM5728-evm).

Information about the TI AM57xx EVM can be found here
http://www.ti.com/tool/tmdxevm5728

The EVM configuration is 1-1 compatible with BeagleBoard X15 with the
additional support for mPCIe, mSATA, LCD, touchscreen, Camera, push
button and TI's wlink8 offering.

Hence, we rename the beagle_x15 directory to am57xx to support TI
EVMs that use the AM57xx processor. By doing this we have common code
reuse. This sets the stage to have a common u-boot image solution for
multiple TI EVMs such as that already done for am335x and am437x. This
sets the stage for upcoming multiple TI EVMs that share the same code
base.

NOTE: Commit eae7ae185335 ("am437x: Add am57xx_evm_defconfig using
CONFIG_DM") introduced DT support for beagle_x15 under am57xx_evm
platform name. However, this ignored the potential confusion arising for
users as a result. To prevent this, existing beagle_x15_defconfig is
renamed as am57xx_evm_nodt_defconfig to denote that this is the "non
device tree" configuration for the same platform. We still retain
am57xx-beagle-x15.dts at this point, since we just require the common
minimum dts.

As a result of this change, users should expect changes in build
procedures('make am57xx_evm_nodt_defconfig' instead of 'make
beagle_x15_defconfig'). Hopefully, this would be a one-time change.

Signed-off-by: Steve Kipisz <s-kipisz2@ti.com>
Signed-off-by: Schuyler Patton <spatton@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Lokesh Vutla <lokeshvutla@ti.com>