Follow flags setting standard of fastboot for boot partitions

[bongbui321]

@bkerler qcom fastboot beside from changing the flags for boot partitions with their specific vendor values such as max_retry, priority, etc... after a successful boot, the boot partitions' flags are also changed:

1. the 54th bit value of the current active boot slot after successful boot is set to 1
2. the 54th bit value of the current inactive boot slot after successful boot is set to 0

This is to achieve the same flag values of boot partitions when using setactive-slot command in fastboot