MIPS: Add platform callback before initializing the L2 cache

Allow platforms to perform platform-specific steps before configuring
the L2 cache. This is necessary for platforms with CM3 since the L2
parameters no longer live in the Config2 register.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10642/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/mips-cm.c

@@ -81,6 +81,13 @@ int mips_cm_probe(void)
 	phys_addr_t addr;
 	u32 base_reg;
 
+	/*
+	 * No need to probe again if we have already been
+	 * here before.
+	 */
+	if (mips_cm_base)
+		return 0;
+
 	addr = mips_cm_phys_base();
 	BUG_ON((addr & CM_GCR_BASE_GCRBASE_MSK) != addr);
 	if (!addr)