MIPS: Allow RIXI to be used on non-R2 or R6 cores

Some processors, like Broadcom's BMIPS4380 and BMIPS5000 support RIXI and the
"rotr" instruction, which can be used to get a slightly more efficient page
table layout.

Introduce a CONFIG_CPU_HAS_RIXI such that those cores can benefit from this
feature. Perform the conditional check updates where relevant.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: john@phrozen.org
Cc: cernekee@gmail.com
Cc: jon.fraser@broadcom.com
Cc: pgynther@google.com
Cc: paul.burton@imgtec.com
Cc: ddaney.cavm@gmail.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12505/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d10ed57..5562ee5 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1996,11 +1996,13 @@
 config CPU_MIPSR2
 	bool
 	default y if CPU_MIPS32_R2 || CPU_MIPS64_R2 || CPU_CAVIUM_OCTEON
+	select CPU_HAS_RIXI
 	select MIPS_SPRAM
 
 config CPU_MIPSR6
 	bool
 	default y if CPU_MIPS32_R6 || CPU_MIPS64_R6
+	select CPU_HAS_RIXI
 	select HAVE_ARCH_BITREVERSE
 	select MIPS_ASID_BITS_VARIABLE
 	select MIPS_SPRAM
@@ -2421,6 +2423,9 @@
 config XKS01
 	bool
 
+config CPU_HAS_RIXI
+	bool
+
 #
 # Vectored interrupt mode is an R2 feature
 #