boot_reason: Add reasons for boot_reason_test.sh

Add "power_on_key" and "power_on_cable" to match
heuristics in system/core/bootstat/bootstat.cpp

Change-Id: I947026d658c8a385aab7a3ade9efacffb9538d56
Signed-off-by: jiajia tang <tangjiajia@xiaomi.com>