MIPS: Fix cacheinfo overflow

The recently added MIPS cacheinfo support used a macro populate_cache()
to populate the cacheinfo structures depending on which caches are
present. However the macro contains multiple statements without
enclosing them in a do {} while (0) loop, so the L2 and L3 cache
conditionals in populate_cache_leaves() only conditionalised the first
statement in the macro.

This overflows the buffer allocated by detect_cache_attributes(),
resulting in boot failures under QEMU where neither the L2 or L2 caches
are present.

Enclose the macro statements in a do {} while (0) block to keep the
whole macro inside the conditionals.

Fixes: ef462f3b64e9 ("MIPS: Add cacheinfo support")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Justin Chen <justin.chen@broadcom.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: bcm-kernel-feedback-list@broadcom.com
Patchwork: https://patchwork.linux-mips.org/patch/15276/

arch/mips/kernel/cacheinfo.c

@@ -17,6 +17,7 @@
 
 /* Populates leaf and increments to next leaf */
 #define populate_cache(cache, leaf, c_level, c_type)		\
+do {								\
 	leaf->type = c_type;					\
 	leaf->level = c_level;					\
 	leaf->coherency_line_size = c->cache.linesz;		\
@@ -24,7 +25,8 @@
 	leaf->ways_of_associativity = c->cache.ways;		\
 	leaf->size = c->cache.linesz * c->cache.sets *		\
 		c->cache.ways;					\
-	leaf++;
+	leaf++;							\
+} while (0)
 
 static int __init_cache_level(unsigned int cpu)
 {