lib: sbi_ipi: Move initial IPI clear to sbi_ipi_init()

sbi_ipi_init() expects the platform warm init function to clear IPIs
on the local hart, but there is already a generic function to do this.
After this change, none of the existing drivers need a warm init
callback.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

include/sbi_utils/ipi/andes_plicsw.h

@@ -32,8 +32,6 @@ struct plicsw_data {
 	uint32_t hart_count;
 };
 
-int plicsw_warm_ipi_init(void);
-
 int plicsw_cold_ipi_init(struct plicsw_data *plicsw);
 
 #endif /* _IPI_ANDES_PLICSW_H_ */