Unify type of "cpu_idx" across PSCI module.

NOTE for platform integrators:
   API `plat_psci_stat_get_residency()` third argument
   `last_cpu_idx` is changed from "signed int" to the
   "unsigned int" type.

Issue / Trouble points
1. cpu_idx is used as mix of `unsigned int` and `signed int` in code
with typecasting at some places leading to coverity issues.

2. Underlying platform API's return cpu_idx as `unsigned int`
and comparison is performed with platform specific defines
`PLAFORM_xxx` which is not consistent

Misra Rule 10.4:
The value of a complex expression of integer type may only be cast to
a type that is narrower and of the same signedness as the underlying
type of the expression.

Based on above points, cpu_idx is kept as `unsigned int` to match
the API's and low-level functions and platform defines are updated
where ever required

Signed-off-by: Deepika Bhavnani <deepika.bhavnani@arm.com>
Change-Id: Ib26fd16e420c35527204b126b9b91e8babcc3a5c
diff --git a/drivers/arm/css/scp/css_pm_scmi.c b/drivers/arm/css/scp/css_pm_scmi.c
index 8dbefa1..b945cda 100644
--- a/drivers/arm/css/scp/css_pm_scmi.c
+++ b/drivers/arm/css/scp/css_pm_scmi.c
@@ -186,7 +186,7 @@
 void css_scp_on(u_register_t mpidr)
 {
 	unsigned int lvl = 0;
-	int ret, core_pos;
+	int core_pos, ret;
 	uint32_t scmi_pwr_state = 0;
 
 	for (; lvl <= PLAT_MAX_PWR_LVL; lvl++)
@@ -196,7 +196,8 @@
 	SCMI_SET_PWR_STATE_MAX_PWR_LVL(scmi_pwr_state, lvl - 1);
 
 	core_pos = plat_core_pos_by_mpidr(mpidr);
-	assert(core_pos >= 0 && core_pos < PLATFORM_CORE_COUNT);
+	assert((core_pos >= 0) &&
+		(((unsigned int)core_pos) < PLATFORM_CORE_COUNT));
 
 	ret = scmi_pwr_state_set(scmi_handle,
 		plat_css_core_pos_to_scmi_dmn_id_map[core_pos],