linux-gbmc: 5.15: Add missing Date: headers to tps53679 patches

Patches are applied with "git am" (via kgit-s2q). Anything git cannot read
out of the patch it invents at apply time: a missing "Date:" becomes the
current wall-clock time, and a missing "From:" becomes
"invalid_git config <unknown@unknown>". Either way the commit SHA -- and so
every descendant SHA, including HEAD -- changes on every build.

That makes the reconstructed kernel source tree non-reproducible. Because
obmc-phosphor-kernel-version bakes HEAD into CONFIG_LOCALVERSION,
KERNEL_VERSION/UTS_RELEASE then changes on every build, while BitBake task
hashes do not, since the SHA is a task output and is never hashed as an
input. An out-of-tree module can therefore take a legitimate sstate hit and
install into /lib/modules/<old-version>, which the running kernel cannot
find:

  modprobe: FATAL: Module dtbocfg not found in directory /lib/modules/...

Give every patch a "From:" and a timezone-qualified RFC 2822 "Date:" in its
mail header block. Dates and authors are taken from each patch body where it
records them, otherwise from the commit that introduced the file. Only
headers are added; no diff content is changed.

Tested: Builds and even with forced builds the hashes match every time
Fusion-Link: fusion2 N/A
Google-Bug-Id: 562061867
Change-Id: I374d19bf6eb28ce20be9cd88763cd4ba38984773
Signed-off-by: William A. Kennington III <wak@google.com>