[nandpart][test] Add unit tests for nandpart.

Change-Id: I6d3324df8781acf0fcd7e2b29331591292076fca
Tested: Ran `runtests -t nandpart-test`

[dev][nandpart][bad-block] Implement bad-block protocol.

bad-block protocol implementation is specific to the methodology used
in the AML u-boot bootloader. We preserve the same semantics so as to
allow the bootloader to continue to read the system partitions even
after additional bad blocks have been grown.

Change-Id: I37954fccf67822459f9c7522c0299a5568c65fb1
Tested: TODO

[dev][nandpart] Initial implementation of NAND partition map driver

Change-Id: Id67e223706ff09c90392483922d5fcc668504bb4
Tested: Manually testd that enumeration works via `dm dump`