Pixelstats: add block layer stats length

The block layer stats format is changing
time by time. This can pass the correct
length by project.

Bug: 219860725
Test: reboot and check log
Change-Id: I760cf211e87fe7cc6069a2379193e61cf323ebb3
diff --git a/pixelstats/service.cpp b/pixelstats/service.cpp
index 4497748..a41d088 100644
--- a/pixelstats/service.cpp
+++ b/pixelstats/service.cpp
@@ -25,6 +25,7 @@
 using android::hardware::google::pixel::SysfsCollector;
 using android::hardware::google::pixel::UeventListener;
 
+#define BLOCK_STATS_LENGTH 17
 #define UFSHC_PATH(filename) "/dev/sys/block/bootdevice/" #filename
 #define UFS_ERR_PATH(err_type) UFSHC_PATH(err_stats/) #err_type
 const struct SysfsCollector::SysfsPaths sysfs_paths = {