MIPS: add MIPS Release 6 build coverage for Boston boards

Now that Travis CI is building with gcc-7.3.0, we can add
build coverage for all combinations of MIPS Release 6
instruction sets (MIPS32, MIPS64, Big Endian, Little Endian).

Add mew default configs for Boston board for all MIPS Release 6
variants.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/configs/boston64r6_defconfig b/configs/boston64r6_defconfig
new file mode 100644
index 0000000..b4bb8a6
--- /dev/null
+++ b/configs/boston64r6_defconfig
@@ -0,0 +1,41 @@
+CONFIG_MIPS=y
+CONFIG_SYS_TEXT_BASE=0xFFFFFFFF9FC00000
+CONFIG_TARGET_BOSTON=y
+CONFIG_CPU_MIPS64_R6=y
+# CONFIG_MIPS_BOOT_CMDLINE_LEGACY is not set
+# CONFIG_MIPS_BOOT_ENV_LEGACY is not set
+CONFIG_MIPS_BOOT_FDT=y
+CONFIG_DEFAULT_DEVICE_TREE="img,boston"
+CONFIG_DISTRO_DEFAULTS=y
+CONFIG_FIT=y
+CONFIG_FIT_VERBOSE=y
+CONFIG_FIT_BEST_MATCH=y
+CONFIG_OF_STDOUT_VIA_ALIAS=y
+CONFIG_SYS_PROMPT="boston # "
+# CONFIG_CMD_ELF is not set
+CONFIG_CMD_GREPENV=y
+CONFIG_CMD_MEMTEST=y
+# CONFIG_CMD_LOADB is not set
+# CONFIG_CMD_LOADS is not set
+CONFIG_CMD_PCI=y
+CONFIG_CMD_SNTP=y
+CONFIG_CMD_DNS=y
+CONFIG_CMD_LINK_LOCAL=y
+CONFIG_CMD_TIME=y
+CONFIG_CMD_EXT4_WRITE=y
+# CONFIG_DOS_PARTITION is not set
+# CONFIG_ISO_PARTITION is not set
+CONFIG_OF_EMBED=y
+CONFIG_ENV_IS_IN_FLASH=y
+CONFIG_NET_RANDOM_ETHADDR=y
+CONFIG_CLK=y
+CONFIG_MTD=y
+CONFIG_MTD_NOR_FLASH=y
+CONFIG_CFI_FLASH=y
+CONFIG_DM_ETH=y
+CONFIG_PCH_GBE=y
+CONFIG_PCI=y
+CONFIG_DM_PCI=y
+CONFIG_PCI_XILINX=y
+CONFIG_SYS_NS16550=y
+CONFIG_LZ4=y