ARM: Add board-specific initialization hook for PSCI

Tegra boards will have to initialize power management for the PSCI
support this way.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/include/asm/psci.h

@@ -34,6 +34,7 @@
 
 #ifndef __ASSEMBLY__
 int psci_update_dt(void *fdt);
+void psci_board_init(void);
 #endif /* ! __ASSEMBLY__ */
 
 #endif /* __ARM_PSCI_H__ */