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/include/plat/common/platform.h b/include/plat/common/platform.h
index 9efb2fd..332cfca 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -237,7 +237,7 @@
 void plat_psci_stat_accounting_stop(const psci_power_state_t *state_info);
 u_register_t plat_psci_stat_get_residency(unsigned int lvl,
 			const psci_power_state_t *state_info,
-			int last_cpu_idx);
+			unsigned int last_cpu_idx);
 plat_local_state_t plat_get_target_pwr_state(unsigned int lvl,
 			const plat_local_state_t *states,
 			unsigned int ncpu);