chip/mt8192_scp: expose PMU-related functions

Exposes PMU-related functions so that we can call the functions to study
some part of cache performance.

BRANCH=none
BUG=b:172988651
TEST=make BOARD=asurada_scp

Signed-off-by: Tzung-Bi Shih <tzungbi@chromium.org>
Change-Id: I27182e3d2af52d8761f45359f3627d70c5acf28c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2567517
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Eric Yilun Lin <yllin@chromium.org>

chip/mt8192_scp/cache.h

@@ -42,4 +42,10 @@ int cache_flush_dcache_range(uintptr_t addr, uint32_t length);
 
 void cache_init(void);
 
+#ifdef DEBUG
+int command_enable_pmu(int argc, char **argv);
+int command_disable_pmu(int argc, char **argv);
+int command_show_pmu(int argc, char **argv);
+#endif
+
 #endif /* #ifndef __CROS_EC_CACHE_H */