utils: fdt: Add fdt helper functions to parse PMU DT nodes

The PMU DT node bindings are defined in docs/pmu_support.md
Add few fdt helper functions to parse the DT node and update the
event-counter mapping tables.

Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>

lib/utils/fdt/fdt_fixup.c

@@ -15,6 +15,7 @@
 #include <sbi/sbi_scratch.h>
 #include <sbi/sbi_string.h>
 #include <sbi_utils/fdt/fdt_fixup.h>
+#include <sbi_utils/fdt/fdt_pmu.h>
 #include <sbi_utils/fdt/fdt_helper.h>
 
 void fdt_cpu_fixup(void *fdt)
@@ -263,6 +264,7 @@ void fdt_fixups(void *fdt)
 	fdt_plic_fixup(fdt);
 
 	fdt_reserved_memory_fixup(fdt);
+	fdt_pmu_fixup(fdt);
 }