MIPS: Allow read64 GCR accessors to work on MIPS32 kernels

If we run a MIPS32 kernel on a system using CM3 we may still need to
access 64 bit GCRs, as will be done in later patches. Allow this by
having the read64_gcr_* accessor functions perform 2 x 32 bit reads on
those systems.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11188/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mips-cm.h

@@ -125,7 +125,17 @@ static inline u32 read32_gcr_##name(void)			\
 								\
 static inline u64 read64_gcr_##name(void)			\
 {								\
-	return __raw_readq(addr_gcr_##name());			\
+	void __iomem *addr = addr_gcr_##name();			\
+	u64 ret;						\
+								\
+	if (mips_cm_is64) {					\
+		ret = __raw_readq(addr);			\
+	} else {						\
+		ret = __raw_readl(addr);			\
+		ret |= (u64)__raw_readl(addr + 0x4) << 32;	\
+	}							\
+								\
+	return ret;						\
 }								\
 								\
 static inline unsigned long read_gcr_##name(void)		\