Device uses heimdall flash method by default, with uppercase
partition name in it's PIT file. This conflicts with flash on update,
because in Linux partitions named in lowercase. To resolve this conflict,
default flash method changed to fastboot. Heimdall still can be used with
`--method` flag: `pmbootstrap flasher --method heimdall-bootimg flash_kernel`
- enable flash on update flag.
- change default flash method to 'fastboot'
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