libavb: Update libavb to current AOSP master

Update libavb to commit 5fbb42a189aa in AOSP/master, because new version
has support for super partition [1], which we need for implementing
Android dynamic partitions. All changes from previous patches for libavb
in U-Boot are accounted for in this commit:
- commit ecc6f6bea6a2 ("libavb: Handle wrong hashtree_error_mode in
avb_append_options()")
- commit 897a1d947e7e ("libavb: Update SPDX tag style")
- commit d8f9d2af96b3 ("avb2.0: add Android Verified Boot 2.0 library")

Tested on X15:

## Android Verified Boot 2.0 version 1.1.0
read_is_device_unlocked not supported yet
read_rollback_index not supported yet
read_is_device_unlocked not supported yet
Verification passed successfully
AVB verification OK.

Unit test passes:

$ ./test/py/test.py --bd sandbox --build -k test_avb

test/py/tests/test_android/test_avb.py ss..s.

[1] https://android.googlesource.com/platform/external/avb/+/49936b4c0109411fdd38bd4ba3a32a01c40439a9

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Eugeniu Rosca <rosca.eugeniu@gmail.com>
Acked-by: Igor Opaniuk <igor.opaniuk@gmail.com>

libavb: Update SPDX tag style

Signed-off-by: Tom Rini <trini@konsulko.com>

avb2.0: add Android Verified Boot 2.0 library

Add libavb lib (3rd party library from AOSP), that implements support of
AVB 2.0. This library is used for integrity checking of Android partitions
on eMMC.

libavb was added as it is and minimal changes were introduced to reduce
maintenance cost, because it will be deviated from AOSP upstream in the future.

Changes:
- license headers changed to conform SPDX-style
- avb_crc32.c dropped
- updates in avb_sysdeps_posix.c/avb_sysdeps.h

For additional details check [1] AVB 2.0 README.

[1] https://android.googlesource.com/platform/external/avb/+/master/README.md

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>

libavb: Update SPDX tag style

Signed-off-by: Tom Rini <trini@konsulko.com>

avb2.0: add Android Verified Boot 2.0 library

Add libavb lib (3rd party library from AOSP), that implements support of
AVB 2.0. This library is used for integrity checking of Android partitions
on eMMC.

libavb was added as it is and minimal changes were introduced to reduce
maintenance cost, because it will be deviated from AOSP upstream in the future.

Changes:
- license headers changed to conform SPDX-style
- avb_crc32.c dropped
- updates in avb_sysdeps_posix.c/avb_sysdeps.h

For additional details check [1] AVB 2.0 README.

[1] https://android.googlesource.com/platform/external/avb/+/master/README.md

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>