bootstat: add 3 pmic off reasons to known set

regular expression:
- "reboot,pmic_off_fault,.*" (175)
- "reboot,pmic_off_s3rst,.*" (176)
- "reboot,pmic_off_other,.*" (177)

regex is dependent on:
https://android-review.googlesource.com/947976



Test: none
Bug: 116838876
Bug: 128929506
Change-Id: I7fae9ecee536f790c8f493c3f5e5f75b03efb1d6
Signed-off-by: Jone Chou <jonechou@google.com>