MIPS: Add generic support for multiple machines within a single kernel

This patch adds a generic solution to support multiple machines based on
a given SoC within a single kernel image. It is implemented already for
several other architectures but MIPS has no generic support for that yet.

[Ralf: This competes with DT but DT is a much more complex solution and this
code has been used by OpenWRT for a long time so for now DT is a bad reason
to stop the merge but longer term this should be migrated to DT.]

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: kaloz@openwrt.org
Cc: Luis R. Rodriguez <lrodriguez@atheros.com>
Cc: Cliff Holden <Cliff.Holden@Atheros.com>
Patchwork: https://patchwork.linux-mips.org/patch/1814/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index f489ec3..2106781 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -883,6 +883,9 @@
 config SYNC_R4K
 	bool
 
+config MIPS_MACHINE
+	def_bool n
+
 config NO_IOPORT
 	def_bool n