u-boot-dra7xx: add latest u-boot from the integration branch

While the code is being pulled from ti-u-boot integration tree, J6/DRA7xx bring up
is being done from a separate branch that does not include all the commits made
for am335x. Hence, until those branches are merged with the mainline and unified
in a single recipe, a separate recipe just for DRA7xx makes more sense. This
recipe should eventually go away and unified under u-boot-ti-staging one.

Signed-off-by: Denys Dmytriyenko <denys@ti.com>
Acked-by: Chase Maupin <chase.maupin@ti.com>

conf/machine/dra7xx-evm.conf

@@ -8,6 +8,11 @@ IMAGE_FSTYPES += "ubi tar.gz"
 
 SERIAL_CONSOLE = "115200 ttyO0"
 
+PREFERRED_PROVIDER_virtual/bootloader = "u-boot-dra7xx"
+PREFERRED_PROVIDER_u-boot = "u-boot-dra7xx"
+
+UBOOT_MACHINE = "dra7xx_evm_config"
+
 # UBI information.  Note that this is board and kernel specific.  Changes
 # in your kernel port may require changes in these variables.  For more
 # details about this board please see
@@ -29,8 +34,6 @@ MKUBIFS_ARGS = "-F -m 2048 -e 126976 -c 3836"
 # UBI: VID header offset:          2048 (aligned 2048)
 UBINIZE_ARGS = "-m 2048 -p 128KiB -s 512 -O 2048"
 
-UBOOT_MACHINE = "dra7xx_evm_config"
-
 # Currently removing the sgx machine feature because there is no SGX package
 # available for omap5
 MACHINE_FEATURES = "kernel26 apm usbgadget usbhost vfat ext2 screen touchscreen"