[Buildroot] linux-firmware: wrong sha256 hash

[Jörg Krause]

Hi,

looks like the hashes for the linux-firmware git repository have
changed:

```
Doing shallow clone
Cloning into 'linux-firmware-17e6288135d4500f9fe60224dce2b46d850c346b'...
warning: redirecting to https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
warning: Could not find remote branch 17e6288135d4500f9fe60224dce2b46d850c346b to clone.
fatal: Remote branch 17e6288135d4500f9fe60224dce2b46d850c346b not found in upstream origin
Shallow clone failed, falling back to doing a full clone
Doing full clone
Cloning into 'linux-firmware-17e6288135d4500f9fe60224dce2b46d850c346b'...
warning: redirecting to https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
remote: Counting objects: 6074, done.
remote: Compressing objects: 100% (73/73), done.
remote: Total 6074 (delta 35), reused 0 (delta 0)
Receiving objects: 100% (6074/6074), 156.40 MiB | 5.05 MiB/s, done.
Resolving deltas: 100% (3756/3756), done.
Checking out files: 100% (1717/1717), done.
warning: refname '17e6288135d4500f9fe60224dce2b46d850c346b' is ambiguous.
Git normally never creates a ref that ends with 40 hex characters
because it will be ignored when you just specify 40-hex. These refs
may be created by mistake. For example,

  git checkout -b $br $(git rev-parse ...)

where "$br" is somehow empty and a 40-hex ref is created. Please
examine these refs and maybe delete them. Turn this message off by
running "git config advice.objectNameWarning false"
ERROR: linux-firmware-17e6288135d4500f9fe60224dce2b46d850c346b.tar.gz has wrong sha256 hash:
ERROR: expected: 28d359523a36c1cdc3e85a8e148bb2d68b036d28b10f0e80a192f3dc29f02c16
ERROR: got     : bf6fe8d7620949a3e771954cb6d9d18dcf000d37ecc910a7cf69723c1798e246
ERROR: Incomplete download, or man-in-the-middle (MITM) attac
```

This is also true for the non-master branches :-(

I wonder if it would help if we switch to non-git downloading the
commit archive from the snapshot URL, e.g.:

-LINUX_FIRMWARE_SITE = http://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git
-LINUX_FIRMWARE_SITE_METHOD = git
+LINUX_FIRMWARE_SITE = https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/snapshot

Best regards,
Jörg Krause