board: Add uCRobotics Bubblegum-96 board support

This commit adds uCRobotics Bubblegum-96 board support. This board is
one of the 96Boards Consumer Edition platform based on Actions Semi
S900 SoC.

Features:
- Actions Semi S900 SoC (4xCortex A53, Power VR G6230 GPU)
- 2GiB RAM
- 8GiB eMMC, uSD slot
- WiFi, Bluetooth and GPS module
- 2x Host, 1x Device USB port
- HDMI
- 20-pin low speed and 40-pin high speed expanders, 6 LED, 3 buttons

U-Boot will be loaded by ATF at EL2 execution level. Relevant driver
support will be added in further commits.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

configs/bubblegum_96_defconfig

@@ -0,0 +1,22 @@
+CONFIG_ARM=y
+CONFIG_ARCH_OWL=y
+CONFIG_TARGET_BUBBLEGUM_96=y
+CONFIG_SYS_TEXT_BASE=0x11000000
+CONFIG_IDENT_STRING="\nBubblegum-96"
+CONFIG_DEFAULT_DEVICE_TREE="bubblegum_96"
+CONFIG_DISTRO_DEFAULTS=y
+CONFIG_USE_BOOTARGS=y
+CONFIG_ARM_SMCCC=y
+CONFIG_BOOTARGS="console=ttyOWL5,115200n8"
+CONFIG_BOOTDELAY=5
+CONFIG_SYS_PROMPT="U-Boot => "
+# CONFIG_DISPLAY_CPUINFO is not set
+# CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_CMD_MD5SUM=y
+CONFIG_CMD_MEMINFO=y
+CONFIG_CMD_CACHE=y
+CONFIG_CMD_TIMER=y
+CONFIG_CLK=y
+CONFIG_CLK_OWL=y
+CONFIG_CLK_S900=y
+CONFIG_OWL_SERIAL=y