arch: add OpenRISC architecture support

Add support for OpenRISC. See here for more details about
OpenRISC http://openrisc.io.

All buildroot included upstream binutils versions are supported.
Gcc support is not upstream, to be able to enable musl C library
support later, we use the branch with musl support.
At the moment it is possible to build a musl based toolchain,
but bootup in Qemu fails.

Gdb is only working to debug bare-metal code, there is no support
for gdbserver/gdb on Linux, yet.

[Peter: drop ?= for GCC_SOURCE]
Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Tested-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

arch/Config.in

@@ -159,6 +159,13 @@ config BR2_nios2
 	  http://www.altera.com/
 	  http://en.wikipedia.org/wiki/Nios_II
 
+config BR2_or1k
+	bool "OpenRISC"
+	select BR2_ARCH_HAS_MMU_MANDATORY
+	help
+	  OpenRISC is a free and open processor for embedded system.
+	  http://openrisc.io
+
 config BR2_powerpc
 	bool "PowerPC"
 	select BR2_ARCH_HAS_MMU_MANDATORY
@@ -378,6 +385,10 @@ if BR2_nios2
 source "arch/Config.in.nios2"
 endif
 
+if BR2_or1k
+source "arch/Config.in.or1k"
+endif
+
 if BR2_powerpc || BR2_powerpc64 || BR2_powerpc64le
 source "arch/Config.in.powerpc"
 endif

arch/Config.in.or1k

@@ -0,0 +1,5 @@
+config BR2_ARCH
+	default "or1k"
+
+config BR2_ENDIAN
+	default "BIG"