plat/arm/sgi: allow value of PLAT_MAX_PWR_LVL to be platform specific

For platforms with multi-threaded CPUs, the number of power domains
supported would be more than the value currently defined by
PLAT_MAX_PWR_LVL. So move the PLAT_MAX_PWR_LVL macro to platform
specific code and let the platform define the number of power domain
levels.

Change-Id: I21c0682e62b397860b2999031a0c9c5ce0d28eed
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
diff --git a/plat/arm/board/sgi575/include/platform_def.h b/plat/arm/board/sgi575/include/platform_def.h
index 394a2e8..16e2898 100644
--- a/plat/arm/board/sgi575/include/platform_def.h
+++ b/plat/arm/board/sgi575/include/platform_def.h
@@ -23,4 +23,6 @@
 /* System power domain level */
 #define CSS_SYSTEM_PWR_DMN_LVL		ARM_PWR_LVL2
 
+#define PLAT_MAX_PWR_LVL		ARM_PWR_LVL1
+
 #endif /* PLATFORM_DEF_H */