mips: Move endianness selection to arch/Kconfig

This option will be used by Microblaze that's why move it to generic
location to be able to use it.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/ceb39fa615cb5657b66a7b77bab99e86ca7a3346.1655299267.git.michal.simek@amd.com
diff --git a/arch/Kconfig b/arch/Kconfig
index 12de8a1..4851300 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -447,3 +447,25 @@
 source "arch/riscv/Kconfig"
 
 source "board/keymile/Kconfig"
+
+if MIPS
+
+choice
+	prompt "Endianness selection"
+	help
+	  Some MIPS boards can be configured for either little or big endian
+	  byte order. These modes require different U-Boot images. In general there
+	  is one preferred byteorder for a particular system but some systems are
+	  just as commonly used in the one or the other endianness.
+
+config SYS_BIG_ENDIAN
+	bool "Big endian"
+	depends on SUPPORTS_BIG_ENDIAN
+
+config SYS_LITTLE_ENDIAN
+	bool "Little endian"
+	depends on SUPPORTS_LITTLE_ENDIAN
+
+endchoice
+
+endif