SPM: Implement SPCI open/close handle SMCs

Introduce SMCs that open and close handles according to the SPCI
specification.

Change-Id: I65f365f15612e01aa445e783e96e48ae275c39fd
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/plat/arm/common/arm_spm_def.h b/include/plat/arm/common/arm_spm_def.h
index 630a29c..5c7ca90 100644
--- a/include/plat/arm/common/arm_spm_def.h
+++ b/include/plat/arm/common/arm_spm_def.h
@@ -138,4 +138,6 @@
 #define PLAT_SPM_NOTIFICATIONS_MAX	U(30)
 #define PLAT_SPM_SERVICES_MAX		U(30)
 
+#define PLAT_SPCI_HANDLES_MAX_NUM	U(20)
+
 #endif /* ARM_SPM_DEF_H */