vexpress/spc: fix a build warning on array bounds

With ARCH_VEXPRESS_SPC option, kernel build has the following
warning:

arch/arm/mach-vexpress/spc.c: In function ‘ve_spc_clk_init’:
arch/arm/mach-vexpress/spc.c:431:38: warning: array subscript is below array bounds [-Warray-bounds]
  struct ve_spc_opp *opps = info->opps[cluster];
                                      ^
since 'cluster' maybe '-1' in UP system. This patch does a active
checking to fix this issue.

Signed-off-by: Alex Shi <alex.shi@linaro.org>
Acked-by: Pawel Moll <pawel.moll@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/mach-vexpress/spc.c

@@ -426,9 +426,15 @@ static int ve_spc_populate_opps(uint32_t cluster)
 
 static int ve_init_opp_table(struct device *cpu_dev)
 {
-	int cluster = topology_physical_package_id(cpu_dev->id);
-	int idx, ret = 0, max_opp = info->num_opps[cluster];
-	struct ve_spc_opp *opps = info->opps[cluster];
+	int cluster;
+	int idx, ret = 0, max_opp;
+	struct ve_spc_opp *opps;
+
+	cluster = topology_physical_package_id(cpu_dev->id);
+	cluster = cluster < 0 ? 0 : cluster;
+
+	max_opp = info->num_opps[cluster];
+	opps = info->opps[cluster];
 
 	for (idx = 0; idx < max_opp; idx++, opps++) {
 		ret = dev_pm_opp_add(cpu_dev, opps->freq * 1000, opps->u_volt);
@@ -537,6 +543,8 @@ static struct clk *ve_spc_clk_register(struct device *cpu_dev)
 	spc->hw.init = &init;
 	spc->cluster = topology_physical_package_id(cpu_dev->id);
 
+	spc->cluster = spc->cluster < 0 ? 0 : spc->cluster;
+
 	init.name = dev_name(cpu_dev);
 	init.ops = &clk_spc_ops;
 	init.flags = CLK_IS_ROOT | CLK_GET_RATE_NOCACHE;