MIPS: add initial infrastructure for Broadcom MIPS SoCs

CFE checks CPU Thread in a different way (using register $22):
mfc0	t1, C0_BCM_CONFIG, 3 # $22
li	t2, CP0_CMT_TPID # (1 << 31)
and	t1, t2
bnez	t1, 2f	# if we are running on thread 1, skip init
nop

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index efe7e44..c30d4ef 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -15,6 +15,7 @@
 
 machine-$(CONFIG_SOC_AU1X00) += au1x00
 machine-$(CONFIG_ARCH_ATH79) += ath79
+machine-$(CONFIG_ARCH_BMIPS) += bmips
 machine-$(CONFIG_MACH_PIC32) += pic32
 
 machdirs := $(patsubst %,arch/mips/mach-%/,$(machine-y))